A: This toothache is killing me.
B: If I am right, this is the third time you’ve had it this month.A: You are right. ().

A. It’s all right.

B. It’ll be gone.

C. I have no method.

D. I’m fed up with it.

关于物体做曲线运动，下述说法正确的是（　　）

A．物体在恒力作用下不可能做曲线运动

B．物体在变力作用下一定做曲线运动

C．速度一定在不断地改变，加速度可以不变

D．做圆周运动的物体的向心力即为其所受的合外力