题目

物体以5m/s的初速度沿光滑斜坡向上减速运动，经4s又滑回原处时速度大小仍为5m/s，则物体的加速度为（） A . 10 m/s2 ， 方向沿斜面向下 B . 5 m/s2 ， 方向沿斜面向下 C . 2.5 m/s2 ， 方向沿斜面向下 D . 0 答案：CIn many countries today, laws protect wildlife. In India, the need for such protection was realized centuries ago.About 300 B.C. an Indian writer described forest that were somewhat like national parks today. The killing of game beasts was carefully supervised(监视). Some animals were fully protected．Within the forest, nobody was allowed to cut timber(wood for building), burn wood for charcoal(炭), or catch animals for their furs. Animals that became dangerous to human visitors were caught or killed outside the park so that other animals would not become uneasy.The need for wildlife protection is greater now than ever before. About a thousand species of animals are in danger of extinction, and the rate of extinction was about one species every fifty years from A.D. 1 to 1800, but now it is about one species every year. Everywhere, men are trying to solve the problem of protecting wildlife caring for the rapid growth of the world’s population1.In forest of ancient India __________A.people were permitted to hunt for funB.only few kinds of animals could be killedC.the killing of game beasts was strictly limitedD.no killing of beasts was allowed．2.Dangerous animals were caught or killed outside the park so as to __________A.keep human visitors safeB.free the rest of the animals from worry or fearC.both A and BD.supply other animals with more food3.The underlined word “extinction” probably means __________A.being hungryB.dying outC.growing slowlyD.being killed4.The example of man’s connection with wildlife protection can date back to _______A.the third centuryB.more than 2000 years agoC.AD.1 to 1800E.over 300 years ago