Why this matters on the SAT
Few grammar questions come up on the SAT as often as this one. Its choices differ only in the punctuation between two words: a period, a semicolon, a comma, a comma plus “and”, or nothing at all. That makes it look like a question about which mark sounds right, but it's really asking one thing: where does one full sentence end and the next begin? Find the two sentences, and most of these take seconds.
Solution to the example
Split the sentence at the blank. Each side has its own subject and main verb (microphones convert, software transforms), so each could stand alone. Two full sentences need a real boundary, and a semicolon is one. The answer is C. D tempts most, because a comma sits where you'd pause, but a comma alone can't hold two sentences apart. “And” without a comma (A) or no mark at all (B) runs them together.
SAT example
In a recording studio, microphones convert air vibrations into electrical _____ audio software then transforms those signals into a digital track that engineers can edit.
Which choice completes the text so that it conforms to the conventions of Standard English?
signals and
signals
signals;
signals,
Every question in this lesson comes down to one test. Split the sentence at the blank and ask of each side: could these words stand alone as a sentence?
Words can stand alone when they have a subject and a main verb (the verb that says what the subject does or is), and no word that makes them lean on another sentence. Grammar books call a group of words like that an independent clause; this lesson calls it a full sentence. In the examples, the subject and main verb, or the word that makes a side lean, are underlined.
Because makes the first fragment wait for more: because the storm knocked out the power, what happened? The second has a verb but no subject: who started? Words like although, when, while and if lean the same way because does.
What the split shows decides the punctuation:
| What the split shows | What can go at the blank |
|---|---|
| Both sides can stand alone | a period, a semicolon, or a comma plus a joining word like “and” |
| One side can't stand alone | a comma, or no mark at all |
A colon can also follow a full sentence, before a second sentence, a list or a phrase that explains it. Colons and dashes come later in the course. The next sections take the table's rows in turn: first two full sentences, then a side that can't stand alone.
Try the split on this question: test each side, then find the choice the table allows.
Practice problem
During a pilot program at a public library, staff extended weekend hours, and visitor numbers rose by nearly twenty-five _____ attributed the boost to a new schedule posted on social media.
Which choice completes the text so that it conforms to the conventions of Standard English?
When the split finds two full sentences, the simplest join is a mark that ends the first one. A period ends it outright; a semicolon ends it and keeps the next one in the same sentence. Either way, the words on each side must stand alone, so, outside a list, a semicolon works only where a period would. In the examples, the words where the two sentences meet are bold.
So when you doubt a semicolon, put a period in its place. After the storm knocked out the power can't stand alone, because after makes it lean on the sentence before, so a period fails there, and the semicolon fails with it.
A comma is a lighter mark. Between two full sentences, a comma and a joining word work only as a pair: the comma, then a joining word such as “and” or “but”.
The comma splice is the one to watch. It sounds fine, because the comma sits right where you'd pause if you read the sentence aloud. But the SAT doesn't punctuate by pauses. Split it at the comma: both sides can stand alone, so a comma by itself isn't enough. The other two wrong versions run the sentences together, one with “and” but no comma, one with no mark at all.
Only a short list of words can do this job. Some others look like joining words, but they aren't:
| Joining words: a comma before them joins two sentences | Look-alikes: a comma before them still leaves a splice |
|---|---|
| “and”, “but”, “so”, “or”, “yet”, “for”, “nor” | “however”, “therefore”, “then”, “also”, “today” |
The look-alikes get their own lesson.
On this question, split at the blank first, then check that the comma and the joining word arrive as a pair.
Practice problem
Two expeditions photographed a total solar eclipse in _____ their measurements indicated that starlight bends as it passes the Sun.
Which choice completes the text so that it conforms to the conventions of Standard English?
Many SAT splices hide behind a short word. When the second sentence starts with it, they, this or she, the words after the comma feel too light to be a sentence of their own. But they can be one. A word like it or they followed by its verb starts a full sentence.
They sold out by noon has a subject, they, and a main verb, sold. It's short and it points back to the loaves, but it can stand alone, so a comma by itself can't join it to the sentence before.
The last version shows the difference one word makes: they → which. Which sold out by noon can't stand alone; it leans on loaves, so a comma is the right mark.
Comma splice or correct? The museum reopened in May, it drew record crowds all summer.
In this question, the words after the blank start with they, so find the verb that follows it before you trust a comma.
Practice problem
Students sometimes picture lysosomes as accidental junk floating in a cell. But the enzymes inside a lysosome can damage the cell if they leak, so the organelle’s membrane must be tightly controlled. For that reason, lysosomes are not random ______ are carefully regulated recycling centers that break down worn-out cell parts.
Which choice completes the text so that it conforms to the conventions of Standard English?
Sometimes a phrase sits where two sentences meet, and it could belong to either one: in one experiment, by noon, built in 1890. A phrase can't join two sentences. Whichever sentence it belongs to, the two still need a real boundary.
The phrase hides the splice. Cross it out, and a comma by itself is left between two full sentences:
The last wrong version moves the phrase into the first sentence, but that doesn't help: the comma after experiment still sits alone between two full sentences.
This SAT question puts a phrase where two sentences meet: cross it out, then check what's left between the sentences.
Practice problem
Some mystery novels build suspense by concealing a crime until the final pages. In contrast, the novel Ash in the Stairwell opens with the narrator’s calm confession and then rewinds to show how the secret was manufactured, a narrative _____ midpoint, the reader is less concerned with who committed the act than with why the characters keep agreeing not to name it.
Which choice completes the text so that it conforms to the conventions of Standard English?
So far, both sides could stand alone. When one side can't stand alone, a period or a semicolon would leave it stranded as a fragment, so it attaches to the full sentence with a comma, or with no mark.
When the new bridge opened has a subject and a verb, but when makes it lean on the sentence before it. Leaving the bridge as the only way across has no subject, and leaving isn't a main verb. An -ing word needs a helper before it can be one: leaving → was leaving. Neither part can stand alone, so a period or a semicolon in front of it leaves a fragment.
The part that leans can come first, too. Then a comma closes it, and the full sentence follows: When the new bridge opened, the ferry stopped running. When the part comes after the full sentence, whether it takes a comma or no mark depends on what it adds; lessons 3 to 5 cover that.
In this question, split at the blank, find the side that leans, and attach it.
Practice problem
Although the materials are inexpensive and the design is not _____ bridge has proven remarkably durable.
Which choice completes the text so that it conforms to the conventions of Standard English?
An -ed word can be a main verb, as in the paint faded, or a word that only describes, as in a faded sign. To tell which, put was or were in front of it. If that gives the meaning the sentence intends, that something was done to the subject, the -ed word was only describing, so it doesn't give that side a main verb.
Its paint faded looks like a subject and a main verb. But the sentence means that years of sunlight did something to the paint, and adding was says exactly that: faded → was faded. So faded only describes the paint, and the words after the semicolon have no main verb. They can't stand alone, so a comma attaches them.
Before you call a side a fragment because it opens with an -ing word or that, look past those words for a main verb. If one comes later, put what in front of it and ask. When the answer is the whole -ing phrase or that clause, it's the verb's subject, so the side can stand alone. A side that opens with when or because still leans, whatever follows.
What had become too expensive? Keeping it afloat. What surprised no one? That it had lost money for years. Each answer is the subject of the verb that follows it, so each side after the semicolon is a full sentence.
A semicolon or a comma at the blank? The lab closed for the summer ______ its equipment needing repairs.
A comma before “and” isn't always right. Outside a list, when the words after “and” have no subject of their own, they can't stand alone, so no comma goes before “and”.
Split it after “and”, and the second side reads flooded the basement. It doesn't say what flooded the basement, so it can't stand alone, and the comma before “and” has to go.
Give the second side a subject of its own, even one that means the same thing, and it becomes a full sentence that needs the comma:
It is the storm again, but it's a subject, so it flooded the basement can stand alone.
Comma or no comma before “and”? The chef tasted the soup ______ and added more salt.
This SAT question offers a comma before “and”, so split after “and” and look for a second subject.
Practice problem
In her workshops on Shakespearean soliloquies, actor-coach Nia Brooks asks students to choose one guiding impulse for each speech. To prevent the delivery from becoming too polished, she prizes ambiguity over ______ trusts the audience to assemble the character’s thoughts.
Which choice completes the text so that it conforms to the conventions of Standard English?
Once in a while, the choices differ in the end mark instead, a period or a question mark, usually with the word order changed too. A direct question puts a verb before its subject and ends with a question mark. A statement ends with a period, and a question it reports keeps the subject first.
To tell which one the blank needs, look at what comes right before the question. When the question words follow a verb in the same sentence with no mark between them, as in wondered whether or investigated how, the sentence reports the question. When the question starts a sentence of its own, or follows a colon, it's asked directly. In these examples, the word order and the end mark are bold.
In the second pair, the rangers aren't asking you anything; the sentence tells you what they wondered, so the question keeps the order of a statement. A part that describes a noun does too, like the dock where the ferry waits. The text around a direct question usually answers it, or says someone set out to find the answer. Check the order and the end mark together: a question asked directly takes question order and a question mark, and a reported one takes statement order and a period.
On this question, check the word order and the end mark together, then look at what comes right before Why.
Practice problem
Rosa Parks was born in 1913 and grew up during a period in United States history when Jim Crow laws enforced racial segregation across the South. A recent biography poses the following inquiry: Why _____
Which choice completes the text so that it conforms to the conventions of Standard English?
Here's the move that makes these questions fast. Look back at the split table: a period, a semicolon and a comma plus “and” all sit in its first row.
Outside a list, each of them is right exactly when both sides can stand alone, so they stand or fall together: if one of them worked at the blank, the others would too. So when two or three of them sit at the same spot in the choices, none of them can be the answer. Cross them all out, and let the split test decide among the choices that are left.
The one exception is rare: a sentence that already separates list items with semicolons. There, one more semicolon would blur the boundary between the two sentences, so only a period works.
That makes one routine for every joining question, the one the worked example and the mixed practice problems follow:
In this question, three choices do the same job, and the words after the blank are built to look like a sentence, so the split has to confirm what the cancel-out leaves.
Worked example
In the museum’s new astronomy gallery, visitors often assume that the “meteorites” in a glass case are the actual rocks recovered from deserts and ice fields. Only after reading the placards do they learn that most of the specimens are ______ surfaces carefully darkened and pitted to resemble the real objects.
Which choice completes the text so that it conforms to the conventions of Standard English?
replicas, and their
replicas, their
replicas; their
replicas. Their
Step 1
The choices differ only in what comes between replicas and their, so this is a joining question. Start with the jobs. The comma plus “and” in A, the semicolon in C and the period in D all do the same job: each says a second full sentence starts at the blank. If one of them were right, the others would be too, so all three cancel out. That leaves B, and the split test has to confirm it.
Step 2
B works only if the words after the blank can't stand alone. Split there, and they read their surfaces carefully darkened and pitted to resemble the real objects.
Here's the trap: darkened looks like a main verb, as in the sky darkened. Run the same test as for the ferry's faded paint: put were in front of it. Their surfaces were carefully darkened and pitted to resemble the real objects says what the text means, because carefully and to resemble the real objects tell you someone did this to the surfaces.
So darkened and pitted only describe the surfaces, the way darkened does in a darkened room. The second side has no main verb, so it can't stand alone, just as the cancel-out said: a comma plus “and”, a semicolon and a period all need a full sentence after them.
Step 3
The first side stands alone: Only after reading the placards do they learn that most of the specimens are replicas, with they and learn as its subject and main verb. The second side describes those replicas and leans on that sentence, so a comma attaches it, with no joining word.
If darkened were a main verb, A, C and D would all be right, which is why they cancel out. C and D tempt most, because a semicolon or a period looks like a clean break. But darkened isn't a main verb, so C and D would leave a fragment, and A's comma plus “and” would have no full sentence to join. The answer is B.
These three questions mix the lesson's cases, and none says which one it tests, so run the whole routine on each: cross out, split, then pick the join.
Practice problem
Music cognition researchers investigated why some people remember melodies more _____ a 2023 study, they asked volunteers to listen to short tunes and later identify them among similar melodies.
Which choice completes the text so that it conforms to the conventions of Standard English?
Practice problem
Astronomers predict the paths of near-Earth asteroids using repeated telescope observations. As new measurements are taken, the predicted path is _____ small differences in the latest data change the calculated orbit.
Which choice completes the text so that it conforms to the conventions of Standard English?
Practice problem
That the mineral pigments on the ceramic fragments had been deliberately heated was clear to archaeochemist Lina _____ determining whether the artisans had precisely controlled the temperature or had merely exposed the minerals to an open flame required a different kind of evidence.
Which choice completes the text so that it conforms to the conventions of Standard English?
Finish the lesson
Finish the remaining questions correctly to complete this lesson.
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