It would be a good idea to use a plastic bottle, ___cut off, as a container to grow young plants in.

A．of which the top

B．the top is

C．the top of which

D．with its top

在计算机体系结构中，CPU内部包括程序计数器PC、存储器数据寄存器MDR、指令寄存器IR和存储器地址寄存器MAR等。若CPU要执行的指令为：MOVR0，＃100（即将数值100传送到寄存器R0中），则CPU首先要完成的操作是（）。

A.100→R0

B.100→MDR

C.PC→MAR

D.PC→IR