螺距(P)是指相邻两牙在中径线上对应两点间的轴向距离，导程(S)是指在同一螺旋线上的相邻两牙在中径线上对应两点间的轴向距离，则双线螺纹的导程与螺距的关系为（ ）。A、P=S/2 B、P=4S C、P=3S D、P=2S
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代号 M16×1.5－5g6g是（ ） 螺纹。A、梯形 B、普通粗牙 C、普通细牙 D、锯齿形
A
B
C
D
啮合齿轮工作图中的两圆柱齿轮的（ ）相切，用细点画线绘制。A、齿顶圆 B、齿根圆 C、大径圆 D、分度圆
A
B
C
D
What's Li's book about?
A. It's about her experiences in learning English.
B. It's about how to get to America.
C. It's about how to answer the questions in the textbook.
D. It's about how to respect other people.
P22 2,5,8题One of the firefighters (消防队员) won a(n)_______ for bravery (勇敢).
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