You can watch TV ______, but you can’t watch it ______ a long time.

A．one, at

B．one, for

C．first, for

D．first, at

（）有叔丁氨基。

A．盐酸麻黄碱

B．重酒石酸去甲肾上腺素

C．盐酸克仑特罗

D．重酒石酸间羟胺

E．盐酸多巴胺