题目内容
坡屋顶是目前民用建筑中采用最普遍的屋面形式，主要以钢筋混凝土屋顶为主。 ()
查看答案
搜索结果不匹配？点我反馈
更多问题
A．wellB．towardsC．tooD．along
The Compass
The great sea voyages of Europe's "Age of Discovery," such as Christopher Columbus's trip to the West Indies in 1492, would have been impossible without the use of a compass. This great device for sea voyages was introduced to the West from China during the thirteenth century A.D. We have to thank ancient Chinese for their invention of the compass.
Two thousand years ago the Chinese had already developed a working compass. A piece of lodestone (天然磁石) would be cut into the shape of a ladle (长柄勺). Placed on a stone board with a smooth surface, the lodestone would move round until the "handle" of the ladle pointed south while the bulk (主体) of the ladle was attracted to magnetic north. This interestingly shaped device is mentioned in a book from about A.D. 80. Other ancient books may have dated it as far back as the fourth century B.C. Jade (玉石) finders played an important role in the invention of the "ladle". They travelled great distances to look for jade. in order not to lose directions, they would take a "ladle" with them.
The jade connection is important. Lodestone is a hard material—though not as hard as some jade. And the making of a magnetic "ladle", as well as a highly smooth stone board, would have required great skill. This suggests that the compass was invented by the jade finders of ancient China.
However, the making of a "ladle" was a tough job. Much work needed to shape a piece of lodestone into a ladle would mean much of its natural magnetism (磁性) had been lost. This again meant that only a few "ladles" could have been produced. Small numbers of ladies produced and growing need for navigation led to a search for ways to produce more compasses, and at the same time, smaller and better compasses.
What is the first paragraph mainly about？
总体和总体单位不得相互转让。 ()
Trees
Trees are useful to man in three very important ways: they provide him with wood and other products; they give him shade; and they help(51)drought and floods.
Unfortunately, in many parts of the world, man has not(52)that the third of these services is the most important. In his eagerness (渴望) to draw quick profit from the trees, he has cut them down in large(53), only to find that with the trees used he has lost the best friends he had. Two thousand years ago a rich and powerful country cut down its(54)to build warships with which to gain itself an empire. It gained the empire but without its trees, its soil became hard and(55). When the empire fell to pieces, the home country found(56)faced with floods and starvation.
Even where a government realizes the.(57)of a rich supply of trees, it is difficult for it to persuade the villager to see this. The villager wants wood to(58)his food with; and he can earn money(59)making charcoal (木炭) or selling wood to the townsman. He is usually too lazy or(60)careless to plant and look after new trees. So, unless the government has a good(61)of control, or can educate the people, the forests will slowly disappear.
This does not only(62)that the villagers' sons and grandsons have fewer trees. The results are even more(63). For where there are trees, their roots break up the soil allowing the rain to sink in and also bind the soil, thus preventing the(64)from being washed away easily. But where there are no trees, the rain falls on hard ground and flows away on the surface, causing floods and carrying away with it the top-soil, in(65)crops grow so well. When all the top-soil is gone, nothing remains but worthless desert.
微信支付 
支付宝支付