Question 164·Medium·Boundaries
The giant sequoia, one of the oldest living organisms on _____ can live for more than three thousand years under the right conditions.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation/boundary questions, first identify the roles of each part of the sentence: find the main subject and verb, then see whether the underlined area is in a nonessential (extra) phrase or between two full clauses. Check what punctuation already appears before or after that phrase and apply the rules: commas, dashes, or parentheses must come in matching pairs around extra information, and semicolons can only go between independent clauses. Quickly test each option by reading the sentence aloud in your head and asking, "Does this create a complete, smoothly punctuated structure?"
Hints
Identify the kind of phrase in the middle
Look at the words between the commas: "one of the oldest living organisms on Earth." Are these words the main idea of the sentence, or are they extra information about "The giant sequoia"?
Think about how extra information is set off
When you put extra descriptive information in the middle of a sentence, what punctuation do you usually put before and after that information?
Match the punctuation you already see
There is a comma after "The giant sequoia" before the descriptive phrase. What punctuation mark after "Earth" would properly close off that phrase so that the sentence reads smoothly into "can live for more than three thousand years"?
Step-by-step Explanation
Understand the structure of the sentence
Read the full sentence with a blank where the underline is:
"The giant sequoia, one of the oldest living organisms on Earth _____ can live for more than three thousand years under the right conditions."
Notice that "one of the oldest living organisms on Earth" is a descriptive phrase giving extra information about "The giant sequoia." This kind of phrase is called nonessential or extra information.
Recall how to punctuate extra information in the middle
A nonessential descriptive phrase in the middle of a sentence must be set off from the rest of the sentence using matching punctuation:
- Usually a pair of commas: one before the phrase and one after it
- Or a pair of dashes
- Or a pair of parentheses
Here, there is already a comma before the phrase (after "The giant sequoia"). We now need punctuation after the phrase, after the word "Earth," to close it off.
Check which punctuation marks can match what is already there
Because the phrase starts with a comma after "The giant sequoia," the cleanest, standard option is to close it with another comma.
A dash after "Earth" would not match the comma that opens the phrase, and a semicolon is not used for setting off descriptive phrases. Leaving out punctuation would leave the middle phrase hanging and make the sentence hard to read.
Also, remember that a semicolon must go between two complete sentences (independent clauses). The part before "Earth" is not a complete sentence by itself.
Choose the answer that correctly closes the phrase
We need punctuation after "Earth" that
- Closes the nonessential descriptive phrase
- Matches the opening comma
- Does not incorrectly suggest a break between two full sentences
Only a comma after "Earth" satisfies all of these rules, so the correct choice is "Earth,".