下列选项中，对减压系统任何部位不注蒸汽的是（）。

A.湿式减压蒸馏

B.湿式常压蒸馏

C.干式减压蒸馏

D.干式常压蒸馏

If a country wants to develop its economy successfully, there has to be a clear______of its social needs.

A．appreciation

B．assurance

C．assumption

D．assessment