【单选题】【消耗次数：1】
对荷载的分类可按时间的变异分类，也可以按荷载作用面的大小分类，以下选项中属于按荷载作用面大小分类的是（）
①
集中荷载
②
永久荷载
③
可变荷载
④
偶然荷载
参考答案：
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【单选题】
阅读理解：阅读下列短文，回答文后问题，选择最佳答案Trees mainly serve man in three important ways: They provide him with wood and other products; they provide him shade; and they help to prevent droughts and floods.Unfortunately, in many parts of the world, man has not realized that the third of these services is the most important．In his eagerness to make money from trees, he has cut them down in large numbers, only to find that without them he has lost the best friends he had. And besides, he is usually too careless to plant and look after new trees. So the forests slowly disappear.This does not only mean that man will have fewer trees. The results are even more serious: for where there are trees, their roots break up soil allowing the rain to sink in and also bind(固定) the soil, thus preventing it from being washed away easily；but where there are no trees, the rain falls on hard ground and flows away, causing floods and carrying away the rich top-soil. When the top-soil is gone, nothing remains but worthless desert.Two thousand years ago，a rich and powerful country cut down its trees to build warships, with which to gain itself an empire．It set up the empire, but, without its trees, its soil became poor and grew weak. When the empire fell to pieces, the home country found itself faced by floods and starvation(饥荒)．2. In many places forests slowly disappear because __________.
①
A. many trees have been cut down by man
②
B. new trees are not well looked after
③
C. man has not paid enough attention to planting trees
④
D. all the above
【单选题】
Rowland Hill was the first to_________ a proposal to use stamps.
①
put forward
②
put up
③
put away
④
put on
【单选题】
Why has jogging become so popular? Because jogging is a very_________ exercise.
①
boring
②
disturbing
③
frustrating
④
interesting
【单选题】
Your long-term memory_________ everythingthat you remember.
①
concludes
②
conveys
③
closes
④
contains