MB是（）的英文缩写。
A.航向信标
B.指点信标
C.全向信标
D.无方向信标
参考答案：B
David apologized to me yesterday. __, I won't forgive him for it was not the first time that he had hurt me.
A．If so
B．If ever
C．Even so
D．Even though
离心水泵水温升高时（）。
A．功率增加
B．流量增加
C．有效汽蚀余量减少
D．必需汽蚀余量减少
