题目

When I was about 12, I had an enemy, a girl who liked to point out my shortcomings(缺点). Sometimes she said I was thin. Sometimes she said I was lazy. Sometimes she said I wasn’t a good student. Sometimes she said I talked too much, and so on. I tried to put up with her as long as I could. At last, I became very angry. I ran to my father with tears in my eyes.     He listened to me quietly, and then he asked, “Are the things she said true or not? Mary, didn’t you ever wonder what you’re really like? Go and make a list of everything she said and mark the points that are tr19．在水平面上有一物体在恒定的水平拉力F作用下移动了一段位移S，第一次在光滑的水平面上，第二次在粗糙的水平面上，则两次运动中拉力F所做的功（　　）A．一样多B．第一次多C．第二次多D．条件不足无法判断