完整的题目为：
---Look!Everything is all in construction!
---Oh,has the building once ＿(built)for exhibition been pulled down,too?
应该填过去分词built,the building和build是动宾关系,所以用过去分词.once built for exhibition为过去分词短语作定语修饰the building.
下面的句子简化一下你会更容易懂：
has the building been pulled down,too?
意思是：那栋楼已经拆了吗?
PS：下一次,问题目,题要给全.