Read the sentence below to find out whether there is any grammatical error in it. The error, if any, will be in one part of the sentence. Choose the option with that part as your answer. If there is no error, choose 'D' as your answer. (Ignore the errors of punctuation, if any).

He enquired me why I had not seen him the previous day as I had promised to do.

A.

He enquired me

B.

why I had not seen him the previous day

C.

as I had promised to do.

D.

No error.

Correct answer is B

why I could not seen him the previous day