题目

听材料，回答问题。 （1） Who does the speaker talk to? A . A friend of his. B . A group of new students. C . A group of visitors. （2） What is the total number of departments in the college? A . Six. B . Five. C . Four. （3） Where do the teachers in the English department mainly come from? A . England and America. B . America and Australia. C . America and Canada.20．质量为M=70kg的人通过光滑的定滑轮拉质量为m=25kg的物体，如图所示，物体以a=4m/s2加速上升时，则人对地面的压力为，g取10m/s2（　　）A．350NB．500NC．650ND．800N