题目

       The eyes are the windows of the soul. Having a pair of bright, clear eyes is very important, so we should protect our eyes throughout our lives.             16     Don’t read while lying down or walking. Relax after every hour of reading.        Keep a distance from the TV set when you watch TV and give your eyes a rest every 30 minutes.        Don’t stare at the sun or try to read in the darkness.      17    This can damage your eyes easily.        Get your eyes checked often. Not many people have this habit, but it is necess如下图是用羊角锤起钉子的示意图，请在图上画出动力F和钉子对锤头阻力的力臂并且说明支点的位置．