一对渐开线齿轮正确啮合的条件是什么?
参考答案:
1)两齿轮的模数必须相等。
2)两齿轮分度圆上的压力角必须相等。
下列各种现象中,不属于生命现象的是( )
A.小鸡破壳而出
B.钟乳石慢慢长大
C.牛吃草
D.蜻蜓点水
_____ that she didn't do a good job, I don't think I am abler than her. [ ]
A. To have said
B. Having said
C. To say
D. Saying