The building has______ floors. And my father's office is on the_______floor.

[　　]

　　A． fifteenth; fifteen

　　B． fifteenth; fifteen

　　C． fifteen; fifteenth

　　D． fifteen; fifteen

　　The building has fifteen floors.(保持原意)

　　________ ________ fifteen floors in the building.

　　The building has fifteenth floors(就划线部分提问)

　　________ ________floors ________ the building ________?

A. to enter　　　　　　     B. enter　　　　　　　　     C. entering　　　　　　　　       D. entered

People built the building ten years ago.(改为被动语态)

　　The building ____ _____ ten years ago.