分离极性中等的甾体类成分宜采用( )

A．聚酰胺色谱
B．硅胶吸附色谱
C．葡聚糖凝胶色谱
D．大孔吸附树脂色谱
E．阳离子交换树脂色谱

Our government ______ all people to save energy and fight against pollution.

A．calls on

B．calls up

C．calls out

D．calls for