计算石油储量所用平均有效厚度的单位名称是：米，它的符号是（）
A.m
B.M
C.km
D.Km
参考答案：A
Speaking of all the songs he has written，I think this is probably his ________ one.(2013·全国Ⅱ)
A．better－known
B．well－known
C．best－known
D．most－known
当离心泵发生气缚或汽蚀现象时，处理的方法均相同
