题目

图中弹簧秤、绳和滑轮的重量均不计,绳与滑轮间的摩擦力不计,物体的重力都是G,在图甲、乙、丙三种情况下,弹簧秤的读数分别是F1、F2、F3,则 A.F3 > F1 = F2         B. F3 = F1 > F2          C. F1 = F2 = F3        D. F1 > F2 = F3 答案：B 解析: 略 －Jack rang you up while you were out．He had something important to tell you． －________? －No, he'll call you later． [　　] A．Shall I call him back B．Will he call again C．What is it about D．Where is he now