Question 9·Hard·Boundaries
Algae blooms can rapidly deplete oxygen levels in coastal waters, a process ______ that often results in massive fish die-offs.
Which choice completes the text so that it conforms to the conventions of Standard English?
For SAT punctuation and boundary questions, first identify the core sentence structure (subject, verb, and any appositive or descriptive phrases). Then decide whether the information in the underlined portion is essential or extra. Apply key rules: do not place commas between a subject and its verb, and do not set off essential "that" clauses with commas. Quickly eliminate any options that break these basic rules, then reread the remaining choice in the full sentence to confirm it sounds clear and grammatical.
Hints
Focus on what the blank is doing
Read the phrase starting at "a process" and ending at "massive fish die-offs." What extra information is being added about "a process" where the blank is?
Check whether the information is essential
Ask yourself: Do we need the words after "that" to know which process is being described, or could they be removed without changing the main meaning?
Use comma rules for clauses with “that”
Remember that essential clauses introduced by "that" usually do not take commas, and commas should not separate a subject from its verb. Look for any option that breaks those rules.
Test each choice by reading it aloud
Plug each option into the sentence and listen for places where a comma forces you to pause in the middle of a logical unit, like between "scientists" and "call." Those are likely incorrect.
Step-by-step Explanation
Understand the sentence structure
Read the whole sentence:
"Algae blooms can rapidly deplete oxygen levels in coastal waters, a process ______ scientists call eutrophication that often results in massive fish die-offs."
The part after the comma — "a process ... that often results in massive fish die-offs" — is an appositive phrase renaming the whole idea of algae blooms depleting oxygen. Inside that phrase, the blank comes right before "scientists call eutrophication."
Identify the clause starting with “that”
The word after the blank in all choices is "that." This "that" introduces a relative clause describing "process."
So we are really deciding how to punctuate the relative clause:
- "that scientists call eutrophication"
We need this clause to stay together and read smoothly, because it tells us which process is being talked about (the one scientists call eutrophication). That makes it essential information.
Apply comma rules for “that” clauses
Key rules you need here:
- Essential clauses introduced by that are not set off by commas.
- You should not put a comma right after "that" to break it away from its clause.
- You should not put a comma between a subject and its verb (for example, between "scientists" and "call").
Use these rules to test each option: any choice that puts a comma right after "that" or between "scientists" and "call" is incorrect. Also, any choice that adds a comma where a restrictive "that" clause follows should be rejected.
Choose the option that follows the rules and reads smoothly
Now check the options:
- Options A and D place a comma immediately after "that," which wrongly breaks up the clause and separates "that" from its subject and verb.
- Option B puts a comma at the end of the phrase, just before another restrictive "that" clause, which incorrectly treats it as nonessential and creates awkward, choppy punctuation.
- Only option C keeps the essential clause together with no extra commas, giving: "that scientists call eutrophication", which correctly and smoothly completes the sentence.