题目

阅读理解 Before I studied psychology, I used to think that people would laugh when funny things occurred. While I was right about that, I discovered there are lots of other psychological factors that make people laugh other than the funny part of a joke. When someone laughs at a joke, there will usually bemore than one reason that makes him laugh—and the more reasons there are, the more powerful the joke will be. I was attending a stand-up comedy show in Egypt, and when the man started to make fun of pedestrians crossing streets, everyone laughed their hearts out. The main reason those p关于力的下述说法中错误的是（ ）A．力总是成对出现的B．力是有大小又有方向的矢量C．两物体间相互作用不一定要直接接触D．力的大小可以用天平测量