An instruction is made up of (41) that specify the function to be performed and operands that represent the data to be operated on. For example, if an instruction is to perform the operation of (42) two numbers, it must know (43) the two numbers are. The processor’s job is to (44) instructions and operands from memory and to perform each operation. Having done that, it signals (45) to send it next instruction.

A．when

B．which

C．where

D．who

若(AX)=0122H，四个标志位CF、SF、ZF、OF的初始状态为0，问执行指令 SUB AX，0FFFH后，这4个标志位的状态是( )。

A．ZF=0，SF=0，CF=O，OF=0

B．ZF=0，SF=1，CF=1，OF=0

C．ZF=1，SF=0，CF=0，OF=1

D．ZF=1，SF=1，CF=1，OF=1