有以下程序

#include <stdio.h>

struct tt

{ int x;struct tt *y;} *p;

struct tt a[4]={20,a+1,15,a+2,30,a+3,17,a};

main()

{ int i;

p=a;

for(i=1;i<=2;i++) {printf("%d,",p->x); p=p->y;}

}

程序的运行结果是

A)20,30,

B)30,17

C)15,30,

D)20,15,