reach.ran wrote:y not choice b, i choose b

if a drug that is already on the market has the potential to help adults who have the same disease, or if it is widely used in childern and the adsense of labelling seems dangerous, the fda can require that the drug undergo pediatric study

a) that the drug undergo

b) that the drug undergoes

this is an example of what is called the command subjunctive, which follows 'command' or 'request' verbs such as demand, request, require, stipulate, etc., as well as functionally equivalent constructions such as it is imperative that..., etc.

the command subjunctive is formed from the same verb form found in the infinitive form of the verb. for instance, 'to be' is an infinitive (and is, are, ... are not), so:
it is imperative that you be on time --> correct
it is imperative that you are on time --> incorrect

the same applies to the question you've posted.

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notice that, in rare instances, both the command subjunctive and the 'normal' form of the verb could conceivably apply. in those cases, you choose based on meaning. for instance:
at yesterday's meeting the councilman proposed that too many tax dollars are spent on local parks --> the councilman expressed his opinion that spending was excessive
at yesterday's meeting the councilman proposed that too many tax dollars be spent on local parks --> i, the speaker/writer, am expressing my opinion that the spending proposed by the councilman is excessive