题目

（1）在图12中用线代表绳子，将两个滑轮连成省力的滑轮组，要求人用力往下拉绳使重物升起．   （2）在图13中画出小球受力的示意图． 答案：The room was too hot. The old man _______ his coat and sat down.A．had on B．put on C．wore D．took off