电液伺服加载系统由（）组成。
A.液压源
B.反馈系统
C.执行系统
D.电源
E、控制系统
参考答案：A, C, E
降水概率为_______，表示“肯定有雨”？[ ]
A．0%
B．50%
C．90%
D．100%
I could hardly understand ______ in class, so I raised my hand to ask.
A．what my teacher said
B．what did my teacher say
C．what has my teacher say
D．what my teacher has said
