运动员用双手握住竖直的滑杆匀速上攀和匀速下滑时，运动员所受到的摩擦力分别是f₁和f₂，那么 [ ]

A．f₁向下，f₂向上，且f₁=f₂

B．f₁向下，f₂向上，且f₁>f₂

C．f₁向上，f₂向上，且f₁=f₂

D．f₁向上，f₂向下，且f₁=f₂

You'll be late for the meeting,         .      [ ]

A. though you don't hurry      

B. or you hurry      

C. if you don't hurry      

D. until you hurry