Make a tentative guess _____ Peking Man _____ have done and used thousands of years ago.

A．that; may

B．that; must

C．what; may

D．what; should

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