决定构件在受力状态下能否安全工作，构件本身材料的力学性能的好坏是其主要因素之一，下列说法正确的是( )。
A．材料强度越高，材质越好，构件越安全
B．材料强度越低，材质越差，构件越便宜
C．材料强度越高，材质越低，构件越经济
D．材料强度越低，材质越好，构件越安全
参考答案：A
解析： 实践中，人们认识到，材料强度越高，材质越好，构件越安全。如，同样粗细的铁棒比木棒结实。
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| In the United States, Monday is the beginning of the workweek(工作周). It is the day most Americans like __1__. And it is certain that the day they like most is Saturday. Saturday is the __2__ of the workweek, and it is the beginning of the weekend. Life is __3__at weekends. Most Americans take care of their houses, cars or gardens. They __4__ the feeling that time seems to move slowly. The workweek is for things you have to, but the __5__is for things you want to do. Some people may get in a car and go for a __6__ in the country. They like to take part in outdoor activities. They __7__ go to a public eating or a film on Saturday night. The __8__ of weekends is a recent invention(近期的发明). In the 1870s, rich people began to speak of __9__ weekends in the country visiting friends. For most people, however, the workday was six days __10__ .
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