Question

Locate the infinitive and identify its use.

Check the turkey to see if it is done.

noun
adjective
adverb

Answer 1

The infinitive in this sentence is to see (if it is done).
It is used as an adverb in this sentence. Check the turkey. Why? To see if it is done. 
When you are answering questions such as when, where, why, it means that you are dealing with adverbs. 

Answer 2

The correct answer is adverb. This is 100% correct.