拨打漫游到海南的外省移动电话是否需要加什么前缀才比较优惠？
参考答案：
不用，直接拨打即可。
I was not quite sure __________.
A．what is she looking for
B．why she came late for school
C．how did she deal with the problem
D．if she has arrived
贮备失效率大于零而小于工作失效率的是（）。
A.热贮备
B.冷贮备
C.温贮备
D.常贮备
