换向阀不换向的原因（）
A.阀体变形
B.弹簧折断
C.电磁铁吸力不够
D.没有油
参考答案：A, B, C
You fool! You __________ all the people in the car yesterday if it had not been for me．You were so drunk while driving!
A．could kill
B．might have killed
C．had killed
D．should have killed
如果背景色和前景色不是默认的黑色和白色可按键盘的哪个键将其恢复为默认前景色和背景色（）
A.D
B.H
C.L
D.E
