Question 42·Hard·Boundaries
Researchers recently identified several new bacteria capable of digesting certain plastics at low temperatures. _____ could help reduce plastic waste in polar regions, where most microbes are inactive.
Which choice completes the text so that it conforms to the conventions of Standard English?
For punctuation and boundaries questions, first identify the grammatical role of the blank (subject, verb, object, etc.), then check how it connects to the surrounding words. Default to no extra punctuation unless there is a clear rule-based reason for it (like setting off a nonessential clause or joining two independent clauses). Read each option in the full sentence and eliminate any that create unnecessary pauses—especially commas or dashes between a basic subject and its verb or that incorrectly set off essential information.
Hints
Identify the role of the blank
Ask yourself: in the second sentence, what part of the sentence does the blank represent—subject, verb, or something else?
Look at the word after the blank
Notice that the word right after the blank is "could." Think about whether there should be punctuation between the subject phrase in the blank and this verb.
Consider the comma placement inside the phrase
When a general noun like "the bacterium" is followed by a specific name, do we usually set that name off with commas, or keep it directly next to the noun?
Test for unnecessary pauses
Read the sentence aloud in your head with each option. Which versions add a pause that feels unnecessary or breaks the flow between the subject and "could help"?
Step-by-step Explanation
Understand what the blank is doing
Read the full sentence with a generic subject in mind:
"Researchers recently identified several new bacteria capable of digesting certain plastics at low temperatures. _____ could help reduce plastic waste in polar regions, where most microbes are inactive."
The blank must be filled with a subject phrase that refers to one of the newly identified bacteria and leads directly into the verb "could help."
Check punctuation between the subject and the verb
In standard English, you normally do not put a comma or dash between a subject and its verb unless you are inserting an interrupting phrase.
Here, we just want a clean subject followed immediately by "could help," so any comma or dash at the end of the blank would create an unnecessary and incorrect break between subject and verb.
Decide if the bacterium’s name should be set off with a comma
The phrase is structured like "the bacterium [specific name]", similar to "the planet Mars" or "the composer Mozart."
When a common noun is followed by a specific identifying name that is essential (it tells you exactly which one), we do not separate the noun and name with commas. Commas would suggest the name is just extra, removable information, which is not the case here.
Match the correct punctuation pattern to the choices
We need a subject phrase that:
- does not end with a comma or dash before "could help," and
- does not insert a comma between "bacterium" and the specific name.
The only choice that fits both conditions is "The bacterium Polaribacter cryofermentans" (Choice A), so that is the correct answer.