人体神经细胞与肝细胞的形态结构和功能不同，其根本原因是这两种细胞的[ ]

A．DNA碱基排列顺序不同

B．核糖体不同

C．转运RNA不同

D．信使RNA不同

I can’t quite remember _____ you started doing the work.[ ]

A. that it was when  

B. when it was that  

C. when was it that  

D. that was it when