单选题Look ! The building 

问题补充：

单选题Look!Thebuildingwhich_________nowwillbeusedasalibrary.A.is being builtB.to be builtC.is builtD.being built

答案：

A解析which _________now是定语从句，根据now，从句谓语要用现在进行时态，且主语which，即The building，和build是动宾关系，所以用现在进行时态的被动语态。选A。