It’s time he _________ piano. Don’t you think he has wasted too much time online?

A．stopped to take up

B．stops taking up

C．stopped to leave alone

D．stops leaving alone

重氮化-偶合反应用于鉴别（）

A.化学结构中含有脂肪氨基的药物

B.具有莨菪碱结构的药物

C.含有酚羟基或水解后产生酚羟基的药物

D.芳酸及其酯类、酰胺类药物

E.具有芳伯氨基或水解后能产生芳伯氨基的药物