sometimes keeps her awake at night is       Tom is getting more and more quiet at home.

A．That;which

B．It;that

C．Whether;what

D．What;that

运用指标对经济周期进行分析，可发现滞后指标的峰顶与谷底总是在经济周期的峰顶与谷底（）出现。

A.同步

B.上方

C.之前

D.之后