盘式制动器的制动力矩靠（）调节。
A.油的压力
B.弹簧的片数
C.螺丝的松紧
D.施闸的速度
参考答案：A
He suddenly appeared on ________ rainy night, which was ________ great surprise to us. [ ]
A. a; /
B. a; a
C. the; a
D. /; the
哪些花卉被称为世界四大切花
