输电线路很短时，装设过电流保护应（）。
A、三段都装；
B、只装Ⅰ、Ⅱ段；
C、只装Ⅱ、Ⅲ段。
参考答案：B
----I passed the college entrance examination.
----Congratulations! You________.
A．could have studied hard
B．must have studied hard
C．should have studied hard
D．might have studied hard
商业保险的构成要素是什么？
