A verb form question tests whether a blank needs a main verb or words that only describe. The main verb says what someone or something does or is. With a new noun after a comma, sort the forms and check the words before the comma. A comma alone can't join two full sentences, so ask what the added words would become. For descriptions, use -ing when the noun does something and -ed when something is done to it.
Hints
- Hint 1
Read the words ending at the comma after design. Find who did what in that part of the sentence.
- Hint 2
Look at the comma before the new noun. If the words after it made a full sentence, what would be needed to join it to the earlier words?
- Hint 3
For methodology, ask whether it does the calibrating or gets calibrated.
Step-by-step
Count main verbs, then check the noun
Step 1Find the complete sentence
Read the research team finalized the experiment's design. Who did what here? The research team is the subject, who or what the sentence is about, and finalized is the main verb saying what it did. These words already make a full sentence, so let's check whether the new noun can have a main verb too.
- Step 2
Check what the comma can attach
Can its methodology take a main verb here? That would make a second full sentence, but no joining word such as and connects it to the first. A comma alone can't join two full sentences; that mistake is called a comma splice. The new noun needs words that only describe it, so this part adds a detail rather than standing alone.
- Step 3
Set aside the forms with helpers
In the version with was, that helper adds a main verb for its methodology. In the version with had been, those helpers make calibrating a main verb too. Each creates a second full sentence, so the comma can't join it to the team’s sentence.
- Step 4
Decide who does the calibrating
Does its methodology do the calibrating, or is it calibrated? The methodology is what someone adjusts, so the describing form must show something done to it. The form carefully calibrating would make the methodology do the adjusting. The form carefully calibrated passes the was test: putting was before it correctly says that something was done to the methodology, so without was the form only describes. Choice C.