齿轮啮合运动，已知i＝5，大齿轮节圆半径为r1，则小齿轮节圆半径r2为（）。
A.5r1
B.1／5r2
C.1／2r1
D.1／4r1
参考答案：B
用画线词的反义词或对应词完成句子。
1. I like _____ hair. I don't like long hair.
2. This room is small. Do you have a _____ one?
3. This tree is very tall, but that tree is _____.
4. I can see the white bird, but I can't see the _____ one.
5. Please stay here. Don't go _____.
What a fine day! How about_______ out for a walk?
A．go
B．to go
C．gone
D．going
