His office is . . . . . . . . the second floor of the building. A. at B. in C. of D. on

The correct answer is: B. in

The preposition “in” is used to indicate a location within a larger space. In this case, the office is located within the building. The other prepositions do not make sense in this context.

• “At” is used to indicate a specific location, such as a street address or a point on a map.
• “Of” is used to indicate possession or association.
• “On” is used to indicate a location on a surface.