下列程序的输出结果是______。
#include
sub1(char a,char b) char c; c=a;a=b;b=c;
sub2(char* a,char b) char c; c=*a;*a=b;b=c;
sub3(char* a,char*b) char c; c=*a;*a=*b;*b=c;
char a,b;
a=’A’ ;b=’B’; sub3 (&a, &b) ;putchar (a) ;putchar (b);
a=’A’;b=’B’;sub2(&a,b);putchar(a);prtchar(b);
a=’A’;b=’B’;sub1(a,b);putchar(a) ;putchar(b);

A．BABBAB

B．ABBBBA

C．BABABA

D．BAABBA