His office is . . . . . . . . the second floor of the building.

Solution (By Examveda Team)

A preposition is a word which comes before a noun or a pronoun and establishes a relationship between the elements of a clause or words. Option D on is correct as it indicates a surface. The other options are wrong as at, in, and of indicate a specific location inside something, and possession respectively. These uses don't fit in the given question.