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