更多"Scientists are trying to make the d"的相关试题:
[填空题]Scientists are trying to make the deserts into good land again. They want to bring water to the deserts so people can live and grow good. They are learning a lot about the deserts. Even so, more and more of the earth is becoming desert all the time. Scientists may not be able to change the deserts in time.
Why is more and more land becoming desert Scientists think that people make deserts. People are doing bad things to the earth.
Some places on the earth do not get very much rain. Yet they still do not become deserts. This is because there are some green plants growing there. Small green plants and grass are very important to dry places. Plants help keep water in the earth. Plants do not let the wind blow the dirt away. Without plants, the land can become a desert much more easily.
A man decides to make a farm in a very dry place. He cuts down the trees. He digs in the earth and takes away the grass and plants that are already growing on the dry land. He makes a farm. H
[单项选择]When scientists are trying to understand a particular set of phenomena, they often make use of a "model." A model, in the scientists’ sense, is a kind of analogy or mental image of the phenomena in terms of something we are familiar with. One example is the wave model of light. We cannot see light as if it were made up of waves because experiments on light indicate that it behaves in many respects as water waves do.
The purpose of a model is to give us a mental or visual picture -- something to hold onto -- when we cannot see what is actually happening. Models often give us a deeper understanding: the analogy to a known system (for instance, water waves in the above example) can suggest new experiments to perform and can provide ideas about what other related phenomena might occur.
An analogy is ______.
A. the study of the universe
B. a Comparison
C. the study of light waves
D. the result of scientific investigation
