一对相互啮合的蜗杆蜗轮，蜗杆的导程角y和蜗轮螺旋角β大小相等，旋向相同。
查看答案
左旋螺旋压缩弹簧可以画成右旋，但必须注明左旋。
A. 对
B. 错
--________?-- I feel happy.
A. How are you
B. How do you feel
C. How old are you
D. How do you do
Which word means " 瑜伽‘’ ？
A. gym
B. yogurt
C. polo
D. yoga
He was _____ a lot.
A. sweat
B. sweated
C. sweating
D. sweats
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