Sentence Correction - Verbal and Reasoning

Directions to SolveWhich of phrases given below each sentence should replace the phrase printed inboldtype to make the grammatically correct? If the sentence is correct as it is, mark 'E' as the answer.
Q1:

He found the gold coin as he cleans the floor.

A as he had cleaned

B while he cleans

C which he is cleaning

D while cleaning

E No correction required

ANS:D - while cleaning

No answer description is available.