治疗慢性贫血（）。

A.浓缩清蛋白液

B.新鲜冷冻血浆（FFP）

C.浓缩血细胞

D.浓缩粒细胞

E.右旋糖酐

Sally took a photo of her friends while they _________ computer games.

A．play

B．are playing

C．have played

D．were playing