坚硬的烟煤普氏系数为（）。
A.f=3
B.f=2
C.f=1.0
参考答案：A
— I find it astonishing that John ______ be so rude to me.
— Not astonishing at all. He is always rude to others.
A．should
B．must
C．might
D．would
库存有何作用？
