2.An exhibition of paintings ____ at the museum next week.
A.are to be held B.is to be held C.are holding D.will hold
3.After the project ____,the engineers immediately started a new one.
A.completed B.has completed C.had been completed D.has been completed
4.We ____ for an hour when the bus finally came.
A.waited B.have waited C.have been waiting D.had been waiting