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:

For some days the new professor lectured above the heads of his pupils.

A over the head of

B over the heads of

C on the heads of

D through the heds of

E No correction required

ANS:B - over the heads of

No answer description is available.