孔口的流速系数φ为（）。
A.0.62
B.0.97
C.0.75
D.0.64
参考答案：B
He tried his best to solve the problem, _____ difficult it was . [ ]
A. however
B. no matter
C. whatever
D. although
Quels sont _____ monuments que vous aimez à Paris
A．des
B．les
C． de
D．/
