GMAT Verbal Tips:

A Sentence Correction question requires you to choose either ‘did not know if the problem could be resolved’ or ‘did not know whether the problem could be resolved’.

Which do you choose?

a.both could be correct
b.only ‘if’ is correct
c.only ‘whether’ is correct

Answer: C

Explanation: In the GMAT, use ‘if’ only in Conditional Sentences. Use ‘whether’ in all other cases.