题目

如图所示，已知电源内电阻r为2Ω，定值电阻R0为3Ω，滑动变阻器阻值范围为0－10Ω．当滑动变阻器R使其阻值为R1时，在R1上获得最大功率，则R1的阻值应为A．2Ω  B．3Ω  C．4Ω       D．5Ω  答案：D解析:略 The twentieth century saw greater changes than any century before: changes for the better, changes for the worse; changes that brought a lot of benefits to human beings, changes that p【1】man in danger. Many things caused the changes, b【2】, in my opinion, the most important was the progress in science.Scientific research in physics and biology has vastly broadened our views. It has given us a deeper k【3】 of the structure of matter and of the universe; it has brought us a better understanding of the nature of life a【4】 of its continuous development. Technology in the application of science has made big advances that have benefited us in n【5】 every part of life.The continuation (持续) of such activities in the twenty-first century will result i【6】 even greater advantages to human beings: in pure science — a wider and deeper knowledge in all fields of learning; in applied science — a m【7】 reasonable sharing of material benefits, and better protection of the environment.Sadly, however, there is another side to the picture. The creativity of science has b【8】 (employ) in doing damage to mankind. The application of science and technology to the development and production of weapons of mass destruction has created a real danger to the continued existence of the human race on this planet.William Shakespeare said, “The web of our life is of a mingled yarn (纱线), good and ill together.” The above brief review of the application of only one part of human activities — science seems t【9】 ( prove ) what Shakespeare said. But does it have to be so? Must the ill always go together with the g【10】? Are we biologically programmed for war?