We used to _____every day when we were children.

A．swim

B．swimming

C．be swimming

D．going swimming

下列哪项属于心功能二级（）。

A.体力活动轻度受限，较重活动出现症状

B.端坐呼吸

C.体力活动明显受限，较轻活动出现症状

D.休息时亦有呼吸困难

E.体力活动不受限