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.

My doctor knew that I would eventually recover and do kind of work I would be doing before

A.

would have been doing

B.

would have done

C.

had been done

D.

had been doing

E.

No correction required

Correct answer is D

No explanation has been provided for this answer.