--What did the teacher say to you just now?  ---She asked me ___.

A．if I hace finished my homework

B．if my homework had finished or not

C．whether or not had I finished my homework

D．whether I had finished my homework

烟气抬升高度公式中，U表示( )。

A．排气筒出口处烟气排出速度

B．排气筒出口处平均风速

C．实际排烟率

D．烟气热释放率指数