— The new equipment has brought us a lot of convenience .

— Yes. It is _____. [ ]

A. usable

B. out of use

C. in much use

D. of much use

以硅胶为固定相的薄层色谱按作用机制属于

A．吸附色谱

B．离子交换色谱

C．胶束色谱

D．分子排阻色谱

E．亲合色谱