＿＿＿the people have become the master of their own country＿＿＿science can really serve the people.

A．It is only then； that

B．It was that； when

C．It is only when； that

D．It was when； then

在进行浅基础内力计算时，应采用下述何种基底压力（）？

A、基底净反力

B、基底总压力

C、基底附加压力