A. IN AL,DX B. OUT 1800H,AX C. XCHG DS,SS D. MOV SS,4000H
A. SUB BX,CXMOV AX,BX B. SUB AX,BXSUB AX,CX C. XCHG AX,BXSUB AX,CX D. MOV AX,BXSUB AX,CX