络筒张力由附加张力、（）、退绕张力组成，其中退绕张力是张力波动的主要因素。

— Can you remember this park? We _____ here.    

— Sure. But now I _____ in that swimming pool. [ ]

A. are used to take a walk, am used to swim 　　

B. are used to taking a walk, am used to swimming 　　

C. used to take a walk, used to swim

D. used to take a walk, am used to swimming