He _____ football regularly for many years when he was young.

A．played

B．was playing

C．has played

D．had played

下列哪种疾病外周血中仅有贫血而无白细胞及血小板的改变（）

A.阵发性睡眠性血红蛋白尿 

B.巨幼细胞性贫血 

C.急性造血功能停止 

D.急性白血病 

E.纯红细胞再生障碍性贫血