1.The Internet allows schools to develop a large amount of learning material that is accessible for students online anytime. There are so many choices of courses and subjects or time frames that completing a program is not an issue for students anymore. We found that online education gives us excellent sources of information, saves our time, money and it is extremely convenient.

答案：有了因特网，学校能够开发出大量的学习材料以供学生随时从网上获取。在网上，学生对各种课程和时间段有多种选择。因此，完成一项教育计划对学生而言就不再成为问题了。我们发现，在线教育为我们提供了绝好的信息资源，节约了时间和金钱，而且十分方便。

2.College students were a major force in the campaign, although participants of all ages were involved. Still, we cannot really credit a handful of individuals for the success of Earth Day. After all, a major message of Earth Day is that every single person has an important role in the environment.

答案：尽管不同年龄的参与者都参与其中，大学生是这些运动的主力军。但是我们确实不能只把地球日的成功归功于一小部分人。毕竟，地球日意味着每一个人在环境保护中都起着重要的作用。

3.But these beliefs about peptide hormones(肽激素)were questioned as laboratory after laboratory found that antiserums(抗血清)to peptide hormones, when injected into the brain, bind in places other than the hypothalamus(下丘脑), indicating that either the hormones or substances that cross-react with the antiserums are present.

答案：但是这些对于肽激素的信仿，被一个又一个的实验室质疑，他们发现抗血清被注入大脑后，并不在下丘脑那里才凝固，显示出肽激素和与抗血清反作用的物质都不存在。

4.In October 1838, I happened to read for amusement Malthus on Population, and being well prepared to appreciate the struggle for existence which everywhere goes on, from long continued observation of the habits of animals and plants, it at once struck me that, under these circumstances, favorable variations would tend to be preserved, and unfavourable ones to be destroyed.

答案：1838年10月，我随便读了《马尔萨散人口论》，很欣赏书的到处都有的生存竞争，经过对动物和植物生存习性的长期观察，我忽然想到这种环境下，有利于生存的变化被保留了，而不利于生存变化被消除了。

5.The best evidence for the layered mantle(地幔)thesis is the well-established fact that volcanic rocks found on oceanic islands, islands believed to result from mantle plumes(地柱)arising from the lower mantle, are composed of material fundamentally different from that of the midocean ridge system, whose source, most geologists contend, is the upper mantle.

答案：分层地幔的证据就是在海岛上发现的火山岩这一明显的事实。岛屿被认为是从低层地幔升起的地柱形成的，它构成的基本成份与海中的山脊系统根本不同，许多地质学家认为它起源于上层地幔。

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