Sorry, there is no Yangzhou Fried Rice now. It _____ only for lunch and supper.

A．serves

B．served

C．is served

D．is serving

筛选是根据药物与杂质的哪项性质不同来分离药物中的杂质（）

A.比重

B.体积

C.浮力

D.色泽

E.气味