为保证电梯正常运行特设置机械安全装置有:().
A.安全钳
B.限速器
C.缓冲器
D.对重
参考答案:A, B, C
--- I had a good holiday at my uncle’s.
--- .
A.Oh, that’s very nice of you
B.Congratulations
C.Oh, I’m glad to hear that
D.It’s a pleasure
某运动员投篮命中率为0.3,求一次投篮时投中次数的概率分布及分布函数.