15. It was with great joy _____ he received the news ______ his lost daughter had been found.

A．because, when

B．which, that

C．since, how

D．that, that

关于预期收益率、无风险利率、某证券的β值、市场风险溢价四者的关系，下列各项描述正确的是（）

A.市场风险溢价=无风险利率+某证券的β值X预期收益率

B.无风险利率=预期收益率+某证券的β值X市场风险溢价

C.预期收益率=无风险利率+某证券的β值X市场风险溢价

D.预期收益率=无风险利率-某证券的β值X市场风险溢价