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问题 不定项选择

如图所示，小球在a点抛出时具有300 J的机械能，其中动能为200 J．小球经过最高点b点，之后经过c点落到地面上的d点（小球未发生形变），a点、c点在同一水平面内，不计空气阻力，则   

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A．小球在b点的动能为200J

B．小球在c点的重力势能为100 J

C．小球在d点的动能为300 J

D．小球在a、b、c三点的机械能均为300 J

答案

BCD

选择题

Great efforts to increase grain production _____ if food shortages are to be avoided. [ ]

A. could be made

B. must be made

C. might be made

D. would be made

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选择题

My parents and I are flying to London for a holiday and I’ll          the chance to practice my spoken English.

A．come up with

B．make use of

C．get along with

D．get tired of
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