单选题 .  In the last century people have accomplished almost unbelievable technological feats. From the invention of the steamship to the development of the spaceship, humankind's mechanical genius has been displayed. A phone is picked up and through a thin, plastic-coated wire, conversation reaches people around the block or thousands of miles away. Television creates images on a glass screen, and soon, through holography (全息照相技术) a screen may not even be needed. This apparent technological mastery has led people to the quite incorrect and dangerous belief that technology can solve any and every problem the environment presents. All that is needed is enough time, effort, money, and know-how.
    But not everything is possible. For instance, unaided humans in their present form could not run a mile in one minute, or anywhere near it. That is believed to be biologically impossible.
    Just as some things are biologically impossible, others are technologically infeasible or improbable. It is not likely that we will solve the world's food problem technologically. Even with the great advances in methods of food production, more people are starving today than ever before. This is partially because population is increasing faster than the research and innovations that compensate for such population growth.
    Technology, for most people, is not the solution to the loneliness or despair, nor will it alleviate (缓解) hatred or prejudice. It can be a tool but not a total cure. In fact, the advanced technologies of modern people might ultimately end our existence, because if technological "progress" is not accompanied by appropriate social change and ecological (生态的) responsibility, people may drown in the poisons of their own industrial wastes.1.  What is the main topic of this passage? ______