In above question i selected answer choice 'D' while OA is 'C'
since high cost and side effects are two things i thought plural verb will be 'drawback' not 'drawbacks'
However in below example:-
She looks unhappy.<== here 'looks' is singular verb.
Can someone explain how to identify such kind of verbs?
First of all 'drawbacks' is not verb here. The verb is 'limit', 'will' represents future tense.
Two things are checked here.
1. Drawback vs Drawbacks
2. of vs to
While preliminary trials have shown marked improvements in blood pressure and blood sugar measurements among most test subjects, many researchers are concerned that the drawbacks to
high costs and of
serious side effects will limit the drug's economic success.
So to be parallel with the bold of, we would choose answer choices with of
2. What are the drawbacks?
>> high costs and serious side effects >>> Multiple issue >> Plural
So we will choose answer choice with drawbacks >> Plural.
Combining 1 and 2, Ans choice C is correct.