下列指令不合法的是( )。A．IN AX，03F9H B．MOV BX，AX C

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问题单项选择题

下列指令不合法的是( )。

A．IN AX，03F9H

B．MOV BX，AX

C．REP CMPSB

D．SHR BX，CL

答案

参考答案：A

解析：因为03F9H已大于255，不能直接寻址，而必须通过DX等寄存器间接寻址。

选择题

--Excuse me, Mr. Li, I don't know the meaning of the whole sentence. What shall I do?

---You'd better first ____ the new words. [ ]

A. look for

B. look up

C. look through

D. look at

单项选择题

James Schneider & Co. have written to us that they are the leading importer in your place dealing ______ chemicals.

A．with

B．in

C．about

D．for