Unlike many mammals, the axolotl retains its larval form throughout _____ and uses this unusual physiology to regenerate entire limbs.
Which choice completes the text so that it conforms to the conventions of Standard English?
For boundary questions, first read the sentence without the interrupting material to confirm the core sentence is complete. If the inserted words are nonessential, you must set them off with matching punctuation on both sides (comma/comma, dash/dash, parentheses/parentheses). Eliminate any choice that (1) doesn’t close what it opens, (2) uses a semicolon without an independent clause on both sides, or (3) mismatches marks (like a colon on one side and a dash on the other).
Hints
Find the core sentence
Read the sentence without the inserted description. If what remains is a complete sentence, then the inserted words are nonessential (extra) information.
Look for matching punctuation
Nonessential interrupting phrases in the middle of a sentence must be set off by matching punctuation on both sides (comma/comma, dash/dash, or parentheses/parentheses). Which option actually gives you a matching pair?
Check whether the interruption is fully closed
After the inserted phrase, the sentence continues with “and uses…”. Make sure the punctuation you choose clearly ends the interruption before the sentence resumes.
Step-by-step Explanation
Identify the core sentence
Remove the interrupting description and read the sentence:
“Unlike many mammals, the axolotl retains its larval form throughout adulthood and uses this unusual physiology to regenerate entire limbs.”
This core sentence is complete, so whatever is added at the blank is extra (nonessential) information.
Determine what punctuation the extra phrase needs
The added material is an interrupting, nonessential explanation (“an unusual biological process, known as neoteny”).
Nonessential interrupting phrases must be set off with matching punctuation on both sides (comma/comma, dash/dash, or parentheses/parentheses).
Eliminate choices that don’t correctly bracket the interruption
- Choice A starts an interruption with a comma after adulthood but does not correctly close it, creating an ungrammatical connection into “and uses…”.
- Choice C uses a semicolon before a mere phrase (not an independent clause) and also fails to use a matching pair.
- Choice D mismatches punctuation (colon to open, dash to close); colons are not used as one half of a bracket around a mid-sentence interruption.
Select the choice with a correct matching pair
Only Choice B uses a matching pair of dashes to bracket the interrupting, nonessential phrase. Therefore, the correct answer is adulthood—an unusual biological process, known as neoteny—.