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问题 选择题

物体在五个恒力作用下，保持匀速直线运动，现去掉其中的一个力，则物体一定做

A．匀加速直线运动

B．匀减速直线运动

C．曲线运动

D．变速运动

答案

答案：D

题目分析：这5个力的合力一定为零，因此撤去一个力以后，其余4个力的合力与这个力等大反向，物体所受合力恒定不变，因此肯定做匀变速运动，是不是直线运动要看合力与速度是不是共线，故选D

点评：本题难度较小，撤去该力后合力与这个力是等大反向的

单项选择题

饭店在客户销售中，往往会根据供求状况和客人住宿时间的长短来决定接受客人预订的先后顺序和优惠程度，这属于饭店收益管理的（）策略。

A．超额预订　

B．时滞控制

C．折扣配置　

D．差异营销
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填空题

The problem is my weight. I’m just 1.57 meters high, but 61. ______
my weight is 75 kilos. Many students often make a fun 62. ______
of me. Some boys were unfriendly for me—they call63. ______
me "meat ball". That makes me to feel unhappy. 64. ______
Although I’m a bit too fat, yet I feel very well. I65. ______
enjoy my meal. I love eating meat very much. And I like 66. ______
sweet food, though. I often have sugar with tea, milk. In 67. ______
the past two months I had put on 5 kilos. So I’m becoming 68. ______
more and more worried this problem, but I don’t 69. ______
know to lose weight quickly. Could you help me, dear doctor 70. ______
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