关于缺铁性贫血，下列哪一项是对的（）

A.血清总铁结合力减低

B.血清转铁蛋白饱和度减低

C.血清转铁蛋白减低

D.红细胞的游离原卟啉减低

E.网织红细胞减低

—Hadn’t your sheep gone much farther _________ you caught up with them?

—No,and we found _________ only two of them that were frozen to death.

A．when;it were

B．until;/

C．as;there was　

D．before;it was 