用哪个选项中的程序段补全程序，可以实现将数据段A中的字符串复制到数据段B中？assume cs:codestack segment dd 8 dup (0)stack endsa segment db "welcome to masm!"a endsb segment db 16 dup (0)b endscode segmentstart: mov ax,stack mov ss,ax mov sp,20h mov ax,a mov ds,ax mov ax,b mov es,ax ? mov ax,4c00h int 21h code endsend start
选项：

A: mov si,0 mov di,0 mov cx,16 cld rep movsb
B: mov bx,16 mov cx,16 mov ax,0s: mov ah,ds:[bx] push ax dec bx pop es:[bx]loop s
C: mov bx,16 mov cx,16 mov ax,0s: mov al,ds:[bx] mov es:[bx],al dec bx loop s
D: mov bx,0 mov cx,16 mov ax,0s: mov al,ds:[bx] mov es:[bx],al inc bx loop s