（10分）一光滑圆环固定在竖直平面内，环上套着两个小球A和B（中央有孔），A与B间由细绳连接着，它们处于如图所示位置时恰好都能保持静止状态，
The first question was difficult , but ___ were quite easy. A. the second B. the other C. another D. the rest
Surely he ____ have forgotten about the wedding! But he has to put business first. A. needn’t B. mustn’t C. can’t
. Luckily, we’d brought a road map without ______ we would have lost our way. A. it B. that C. this D. which
许多科学家在物理学发展过程中做出了重要贡献，下列表述正确的是（ ） A．牛顿最早指出力不是维持物体运动的原因 B．笛卡尔对牛顿第一定律
29. A good teacher should leave some time for the students to _________ the knowledge. A. introduce B. receive C. digest D. Accept
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