Question 170·Medium·Boundaries
Considered a pioneering computer scientist, Alan Turing proposed the concept of a hypothetical machine that could perform any computation given enough _____ idea laid the groundwork for the modern theory of algorithms.
Which choice completes the text so that it conforms to the conventions of Standard English?
For clause-boundary questions, first test whether the words on each side of the blank are complete sentences. If both are independent clauses, eliminate options that use only a comma (comma splice) or that add conjunctions which create illogical or ungrammatical structures. Then choose punctuation that matches the relationship: use a colon when the second clause explains, restates, or emphasizes the first; otherwise expect a semicolon, period, or comma + coordinating conjunction. Always read the full sentence with the choice inserted to confirm both grammar and meaning.
Hints
Check completeness of each part
Ask yourself whether the words before the blank and the words after the blank could each stand alone as full sentences.
Think about what the second part is doing
Is the part starting with "his idea laid the groundwork" explaining or expanding on the idea before the blank, or is it supposed to show a cause, a list, or something else?
Match the punctuation to the relationship
Once you know both sides are complete sentences and the second explains the first, think about which punctuation mark is used to introduce an explanation or elaboration after a complete sentence.
Watch out for comma splices
Be cautious of answers that leave only a comma between two complete sentences—that is almost always incorrect on the SAT.
Step-by-step Explanation
Understand the sentence structure
Read the full sentence with a pause at the blank:
"Considered a pioneering computer scientist, Alan Turing proposed the concept of a hypothetical machine that could perform any computation given enough _____ idea laid the groundwork for the modern theory of algorithms."
Before the blank, we have a complete idea about what Turing proposed. After the blank, we have another complete idea: "his idea laid the groundwork for the modern theory of algorithms."
Identify clause types on both sides
Check if each side of the blank could stand alone as a sentence:
- Before the blank: "Alan Turing proposed the concept of a hypothetical machine that could perform any computation given enough time." → This is a complete sentence.
- After the blank: "his idea laid the groundwork for the modern theory of algorithms." → This is also a complete sentence.
So we are connecting two independent clauses, and the second one restates or explains the importance of the first.
Recall punctuation rules for connecting clauses
When you have two independent clauses, here are the correct ways to connect them:
- Period: two separate sentences.
- Semicolon: links two closely related complete sentences.
- Comma + coordinating conjunction (and, but, so, etc.).
- Colon: if the second clause explains, summarizes, or gives more detail about the first.
A single comma between two complete sentences is wrong (comma splice). Adding "and" or "because" also changes the meaning and must fit logically and grammatically.
Test each answer choice
Insert each option into the sentence and check grammar and logic:
- "time, his" → "...time, his idea laid..." connects two complete sentences with only a comma. That is a comma splice.
- "time and his" → "...time and his idea laid..." incorrectly joins the clauses; this creates a confusing structure where "and" tries to link verb phrases but introduces a new subject "his idea" without proper punctuation.
- "time because his" → "...time because his idea laid..." makes it sound like Turing proposed the concept because his idea laid the groundwork, which is a backward and illogical cause-and-effect.
- "time: his" → "...time: his idea laid..." correctly uses a colon after a complete sentence to introduce an explanation.
Correct answer: time: his.