-----Did Mary come to the party?

---I don’t know．She _____while I was out．

A．may have come

B．must have come

C．might come

D．could come

项目( )是工程经济评价工作的重要组成部分，同时也是寻求合理决策的必要手段。

A．独立型方案比较

B．互斥型方案比较

C．互补型方案比较

D．现金流量相关型方案