男性，45岁，因慢性肾衰竭行维持性血液透析治疗已有3个月，尿毒症症状明显减轻，但血红蛋白70g/L。本例贫血的主要原因是（）

A.尿毒症毒素抑制骨髓

B.透析失血及缺铁

C.叶酸及维生素B缺乏

D.红细胞寿命缩短

E.促红细胞生成素减少

30．It was the training that he had as a child________made him such a good pianist, received by teenagers as well as adults．

A．that

B．which

C．who

D．What