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.

By such time you finish that chapter, I will write a letter.

A.

The time when

B.

By the time

C.

By that time

D.

The time

E.

No correction required

Correct answer is B

No explanation has been provided for this answer.