Question 168·Hard·Form, Structure, and Sense
After carefully cataloging the seasonal growth rings in hundreds of ancient driftwood samples, _____
Which choice completes the text so that it conforms to the conventions of Standard English?
For modifier-intro questions (e.g., starting with "After...," "Having...," or "While doing..."), first identify the action in the introductory phrase and then make sure the first noun after the comma is the one that logically performs that action. Quickly eliminate any answer where the modifier "dangles" (seems to describe the wrong thing) or where the sentence becomes wordy and unclear due to unnecessary passive voice or awkward rearrangements; usually the best choice is the clearest, most direct active-voice option that fixes the modifier.
Hints
Match the doer of the action
Focus on the phrase before the comma: "After carefully cataloging the seasonal growth rings...". Which choice makes it clear who did that cataloging?
Watch for dangling modifiers
The noun right after the comma should be the one that did the cataloging. Eliminate any option where the first thing after the comma could not logically catalog samples.
Prefer clear, active wording
Between grammatically acceptable options, favor the one that uses a clear, active subject–verb structure rather than a long, awkward passive construction.
Step-by-step Explanation
Identify what the opening phrase is modifying
Look at the beginning of the sentence: "After carefully cataloging the seasonal growth rings in hundreds of ancient driftwood samples, _____."
That introductory phrase describes an action someone performed: carefully cataloging the seasonal growth rings. The noun that comes right after the comma must be the one that did this action.
Check each option for a logical subject
Ask for each choice: Who is the one cataloging the seasonal growth rings?
- In some choices, the first noun after the comma is several abrupt warming periods or the Larsen Ice Shelf or an empty pronoun like it.
- Warming periods and an ice shelf cannot catalog growth rings, and "it" does not clearly refer to a doer of the action.
You need a choice where the noun right after the comma can reasonably be the one doing the cataloging.
Eliminate dangling modifiers and awkward passive constructions
Choices that make the warming periods, the ice shelf, or a vague "it" seem like they did the cataloging create a dangling modifier, which is ungrammatical. Also, some options bury the main idea in passive voice and wordy phrasing ("were determined by the research team," "was determined by the research team").
The best answer will:
- Put the research team right after the comma (they are the ones who cataloged the rings), and
- Clearly state what they concluded, in straightforward active voice.
Select the choice that is logical, clear, and concise
Only one option makes the subject after the comma be the research team, clearly tying them to the cataloging action and expressing their conclusion in clear active voice:
Correct answer: D) the research team determined that the Larsen Ice Shelf had experienced several abrupt warming periods during the last millennium.