Ex.1 Suggest a suitable title for each paragraph of the passage

Ex.2 Express the main idea of each paragraph in a single sentence in English.

Text Craters of the moon

The dominant surface features of the Moon are nearly circular craters which most American specialists believe are chiefly the result of meteoroid impact. Some of the large basins now filled with dark material are believed to have been formed by impact of bodies of asteroidal size. Infall of meteoroids has probably been going on throughout lunar history. Even though erosion by water changed the appearance of the older craters with respect to the younger ones. This change can probably be attributed to such factors as solar radiation, extreme temperature changes, micro-meteorite bombardment, Moon-quakes, and burial of older features with thin layers of material ejected from younger craters.

Three general classes of craters may be recognized. Those which are at the foci of bright radiating streaks, called ray craters, are the most conspicuous craters on lunar surface at full moon. The rays are believed to be discontinuous layers of highly reflective material derived primarily from the craters from which they radiate. These are among the youngest craters on the Moon. Although the rays show up under high sun, they are rarely visible at very low sun. At low sun the topographic details of the craters are clearly visible.

Craters of Class II exhibit topographic features at low sun similar to those of Class I, but under high sun exhibit no ray patterns. The rays evidently darken and disappear with time and craters of Class II are older than ray craters. As the craters become older even talus slopes apparently stabilize and darken as light bands are rarely visible in the oldest craters.

Craters of Class III, the oldest, have been considerably modified and their walls have been dissected. In many places younger craters are superimposed upon them. Under high sun these old craters can be seen only with difficulty.

A sequence of craters exhibiting progressively modified features can be recognized that spans the range of ate from bright young ray craters to the oldest recognizable craters. The classification of lunar craters by age leads to certain inferences concerning the geologic history of the Moon.

Ex.1 Arrange the words to form a sentence.

1. classify, craters, scientists, into three general classes. 2. at full noon, ray craters, on lunar surface, are the most conspicuous craters. 3. at low sun, craters of Class II, topographic features, exhibit. 4. can be seen , under high sun, old craters, with great difficulty.

Ex.2 Answer the questions in short simple sentences. Your paragraph should not exceed 120 words.

1. What are the dominant surface features of the Moon? 2. How are these craters believed to have been formed? 3. Is the appearance of all the craters identical? 4. What factors can the change in the appearance of craters be attributed to? 5. What are the most conspicuous craters on lunar surface?

Text How is soil formed?

If the surface of our earth were not covered with soil, man would perish. Without soil, plants could not grow and human beings and other animals would have no food.

Soil is the loose, powdery earth in which plants grow. It is made up of very small pieces of rock and decayed plant and animal materials. The small pieces or particles of rock were once parts of larger rocks. The plant and animal materials come from plant and animal bodies.

No rock is so hard that it cannot in time be broken into pieces. The crumbling and wearing away of rock, which is called “weathering”, goes on all the time and is done in many ways. Glaciers push great piles of rocks ahead of them as they move along and this pushing and grinding help crumble the rocks.

Water with chemicals in it will dissolve and wear away some kinds of rocks. Changes in temperature often help break rocks into small pieces. The heating and cooling of rocks may cause cracks to appear. Water gets into the cracks, freezes, and cracks the rocks even more. Even plant roots may cause rocks to break. Sometimes the seeds of trees fall into cracks in rocks, the seeds sprout, and as the roots of the plant grow, they help split the rock. Wind also helps crumble rocks by hurling sand against the rocks.

But this is only the beginning of soil-making. To make real soil, the sand or fine particles of rock must have “humus” added to it. Humus is an organic material that comes from plants and animal bodies. The bodies of almost all dead land plants and animals become a part of soil, through the work of bacteria.

Bacteria cause the plants and animals to decay and make the soil fertile. Earthworms and many kinds of insects help to make the soil rich. The richest layer of soil is at the top and is called “topsoil”. This has much humus in it. The next layer, which is called “subsoil”, contains mostly bits of rock. The layer beneath is bedrock, which is under the soil everywhere.

Ex.1 Think and answer

1 Why is soil so important for man?

2 What is soil?

3 What is the composition of soil?

4 What is weathering?

5 How do glaciers work?

6 How does temperature help break rocks?

7 How does water help weathering?

8 How do plant roots cause rocks to break?

9 How do seeds help split the rocks?

10 What components are needed to make soil fertile?