John spent a lot of time ________to his colleagues how challenging the project was.
A. explain
B. explaining
C. to explain
D. explained
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It is the high efficiency of the new equipment ___ has increasingly attracted our attention.
A. which
B. what
C. that
D. who
摩擦型带传动是依靠()来传递运动和动力的。
A. 带和带轮接触面之间的正压力
B. 带与带轮之间的摩擦力
C. 带的紧边拉力
即将打滑时,传动带所能传递的最大有效拉力Ftmax和()有关系。
A. 带的长度
B. 带轮的直径
C. 带在带轮上的包角
D. 带的重量
V带传动中,带的弯曲应力作用在()处。
A. 带和带轮接触弧段
B. 带的紧边
C. 带的松边