题目

What does Mr. King do?A.A doctor. B.A teacher. C.A manager. 答案：【答案】B【解析】【原文】W: Hello! Could I speak to Mr. King, please?M: Sorry. He is giving his students a lesson now. Would you mind calling back later?如图所示，用方向不变的力F，将杠杆从A位置匀速提升到B位置的过程中，F的大小变化情况有（ ）A．保持不变B．逐渐变小C．逐渐变大D．无法判定