题干

该图示意某国乡村人口和城市化水平的变化,读图回答22~23题。

【小题1】1990年该国城市人口大约是  (     )
A.2亿B.2.9亿C.3.8亿D.4.7亿
【小题2】有关该国人口和城市化的叙述,正确的是 (     )

A:1961年到1976年乡村人口增加,城市人口减少

B:1976年以前乡村人口增长速度比1976年以后更快

C:1961年到1990年乡村人口和城市人口的增长速度相当

D:1961年到1990年城市化进入加速发展阶段

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答案(点此获取答案解析)

B

同类题1

阅读理解

B

    Researchers say they have created a new super-tough material in the laboratory. It is stronger, lighter and costs less than steel. But the new material is not a product of high technology. It is wood. Researcher Liangbing Hu says that it can compete with some of the world's strongest materials or even replace steel.

    The product is called Super Wood. It doesn't require any special raw, unprocessed material. That means the cost of the product will be relatively low.Hu said, “We can start with very cheap wood, and also very fancy, expensive wood. But in the end, we get very similar performance.”

    Super Wood is made by partially removing a natural polymer called lignin(木质素). Hu explained, “Lignin is like glue to hold all the parts together in natural wood. To be able to densify(增密)the wood completely, some of the lignin has to be removed. “Strong chemicals are put on the wood to remove about half of its lignin. Then, after being left in extreme heat and pressurized for a day, the treated wood is ready.

    The wood is strong enough to build automobiles, airplanes, wind turbines and more. Researchers are finding many new ways to use wood, including creating batteries and see-through wood and paper.Hu said, “Wood has been existing on Earth for more than a million years. And human beings have been using wood for furniture, construction for more than 10 thousand years. And the more we worked on this material, we realized, we have never fully exhausted the potential of this amazing material.”