读图回答下列问题：

A —— salesgirl         B —— customer
A: Good afternoon, can I help you?
B: Yes, ____ 
A: We have different kinds of sports shoes. They’re all in style. What color would you like?
B: I prefer blue.
A: ____ ?
B: Size 40.
A: What do you think of this pair?
B: Great! ____  ?
A: Certainly. This way, please.
B: Oh, they fit me very well. ____ ?
A: 500 Yuan.
B: ____ . I can't afford.
A: Well, I'll give you a 20% discount.
B: OK. I'll take them.

做匀速圆周运动的物体，如果合外力减小，物体将脱离原来的轨道做____运动；如果合外力增大，物体将脱离原来的轨道做____运动；如果合外力突然消失，物体将沿着轨迹____方向做匀速直线运动．