The new building over there is our library(对our library提问)

The new building over there is our library(对our library提问)
（What ）（is ）that new building over there?
（那边那栋新楼是什么?）what是错的，我填了没错，就是what了。请你想想，疑问词when（何时）, where（何地）, how（怎样）, who（谁）, whose（谁的）, why（为何），有哪个能指代our library？一个都不可能！