执行MOV AX ，WDAT 指令，要使AX寄存器中内存为3412H，不能采用下列哪种数据定义？
A． DSEG SEGMENT
WDAT EQU WORD PTR BDAT
BDAT DB 12H，34H
DSEG ENDS
B． DESG SEGMENT
BDAT DB 12H，34H
WDAT = WORD PTR BDAT
DSEG ENDS
C． DESG SEGMENT
WDAT EQU THIS WORD
BDAT DB 12H，34H
DSEG ENDS
D． DESG SEGMENT
BDAT DB 12H，34H
WDAT LABEL WORD
DESG EBDS
