最能表明细胞间功能差异的是[ ]

A．细胞核的大小

B．细胞体积的大小

C．细胞器的种类和数量

D．细胞膜的结构和功能

— That must have been a long trip. 

— Yeah, it _____ us a whole week to get there.

A．takes

B．had taken

C．took

D．was taking