The expert offered us another piece of advice , ___ of great help to our program.

A．I think it is

B．I think which is

C．which I think it is

D．which I think is

患者屈膝仰卧位适用的引流部位是（）

A．上叶前面支气管

B．舌叶前面支气管

C．上叶肺尖支气管

D．下叶尖段支气管

E．下叶内侧基底段支气管