The room _____, but now it's dirty again. [ ]

A. was cleaned

B. is cleaned

C. cleaned

D. cleans

对非国家投资项目而言，投资者在确定基准收益率时应以（）为基础。

A．资金限制和投资风险

B．资金成本和机会成本

C．目标利润和投资风险

D．资金成本和通货膨胀