题目

如图所示，一幼儿园小朋友在水平桌面上将三个形状不规则的石块成功叠放在一起，受到老师的表扬。下列说法正确的是 （） A . 石块b对a的支持力与a受到的重力是一对相互作用力 B . 石块b对a的支持力一定等于a受到的重力 C . 石块c受到水平桌面向左的摩擦力 D . 石块c对b的作用力一定竖直向上 答案：DA: Hello, Bob! How is it going?B: Hello, Kate!【1】And you?A: Very well. What's your plan for the summer?B: I had a Chinese course last year, and I'd like to go on with it his summer.A: How was the course?【2】B: Yes. It seemed that way at first. But after a while it became easier.A: You were the best in the class, right?B: I did get an A. Well, could you tell me your summer plan?【3】A: No, not this summer.【4】B: That must be very interesting. Can I go with you?A:【5】Oh, there comes the bus! Good-bye!B: Bye-bye!A.I plan to go to Africa next summer.B.Will you travel somewhere interesting?C.No problem.D.Is Chinese very difficult?E.I'm OK.