Which of the phrases given below the sentence should replace the phrase printed in bold type to make it grammatically correct? If the sentence is correct as it is, mark 'E' as the answer.

The crops are dying; it must not had rained.

A.

must had not

B.

must not be

C.

must not have

D.

must not have been

E.

No correction required

Correct answer is C

No explanation has been provided for this answer.