[单选题]以下选项中，不能对主函数中变量i和j的值进行交换的程序是（　　）。

A#include <stdio.h>void swap(int *p, int *q){　int *t;　*t = *p;　*p = *q;　*q = *t;}main(){　int i=10, j=20,*a=&i,*b=&j;　swap(a,b);　printf(i=%d j=%d,i,j);}

B#include <stdio.h>void swap(int *p, int *q){　int t;　t = *p;　*p = *q;　*q = t;}main(){　int i=10,j=20,*a=&i,*b=&j;　swap(a,b);　printf(i=%d j=%d,i,j);}

C#include <stdio.h>#include <stdlib.h>void swap(int *p, int *q){　int *t;　t = (int *)malloc(sizeof(int));　*t = *p;　*p = *q;　*q = *t;　free(t);}main(){　int i=10,j=20;　swap(&i,&j);　printf(i=%d j=%d,i,j);}

D#include <stdio.h>void swap( int *p, int *q){　int t;　t = *p;　*p = *q;　*q = t;}main(){　int i=10,j=20,*x=&i,*y=&j;　swap(x,y);　printf(i=%d j=%d,i,j);}