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问题 单项选择题

图14-24所示桁架结构1杆轴力一定为（）。

 

A. 拉力

B.压力

C. 零

D. 需要给出内部三个铰的位置才能确定具体受力性质

答案

参考答案：C

解析：

取内部三角形为隔离体，可计算内外部三角形的三个连接杆件轴力均为零，因此1杆轴力也为零，故正确答案选择C。

完形填空

B

Just now, I entered the website “Topic for Today”, I feel   36   (interest) in the report on middle school students’ using cell-phones on campus．In fact, many students now come to school   37   cell-phones．My schoolmates have different opinions．Some think   38   is convenient to get in touch with others with the cell-phone, which also makes you feel safe especially in time of trouble．  39   , it is nice to enjoy various functions of different cell-phones． 40   think differently．First, the cell-phone is not   41   must in school, as   42   are some IC phones in the school   43   (make) it easy to call others．Second, many students often play e-games and send e-messages with their cell-phones, even in class,   44   will surely have bad effects on their study．What’s more, it will result in a great waste of time and money．In my opinion, the cell-phone is a   45   (use) tool in our daily life．But it doesn’t mean we can use it freely in school．
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单项选择题

给下列建筑物供暖时，散热器必须暗装或加防护罩的是（）

A.医院病房

B.办公室

C.幼儿园

D.厂房车间
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