欲使在固定斜面上匀速下滑的物体静止，可采取的方法是

题干

A：在物体上叠放一重物

B：对物体施加一垂直于斜面的力

C：对物体施加一竖直向下的力

D：增大斜面倾角

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B

A: You have nice teeth, Lily. You must take good care of (好好爱护) them.

B: Thank you. I try! ____.

A: Yes, I talked to him after he went to see a dentist.

B: He went to the dentist? ____

A: Why is that great?

B: He had a toothache (牙痛) yesterday. I told him to go to a dentist. ____

A: Brush your teeth two or three times a day.

B: What e/se (别的) did the dentist say?

A: Get a new toothbrush every three or four months.

B: Didn't the dentist tell Ken anything else?

A: ____

B: Yes, but what about Ken's tooth? ____

A: Oh! The dentist found a small piece of food under Ken's gums (牙龈). Ken needs to floss (用牙线剔牙) every day.

B: Wow. He just needed to floss!

A. That's great!

B. What's the problem?

C. Visit the dentist often.

D. What did the dentist say?

E. He couldn't sleep well because of it.

F. How often does he ~visit the dentist?

G. Hey, Susie, did you see Ken this morning?