--- Is there any flowers _______ the tree.

--- No. But there are many birds _________ it.

A．in, on

B．in, in

C．on, in

D．on, on

肾移植选用硬膜外阻滞优点有（）。

A.便于与患者交流

B.易于呼吸管理

C.出血少

D.避免肌松药副作用

E.以上都不是