The last time I _________ her,she _________at a medical college.

A．was visiting;studied

B．visited;studied

C．visited;was studying

D．was visiting;was studying

下列哪项不是细胞衰老的特征（）

A.细胞内水分减少

B.细胞呼吸速率减慢

C.细胞内色素积累较多

D.细胞膜通透性不变，物质运输功能增强