有以下程序：
#include ＜stdio.h＞
main()
FILE *fp; int i,a[6]=1,2,3,4,5,6;
fp= fopen("d3.dat","w+b");
fwrite(a,sizeof(int),6,fp);
fseek(fp，sizeof(int)*3，SEEK_SET); /*该语句使读文件的位置指针从文件头向后移动3个int型数据*/
fread(a,sizeof(int),3,fp); fclose(fp);
for (i=0; i＜6; i++) printf("%d,",a[i]);

程序运行后输出的结果是( )。

A．4,5,6,4,5,6,
B．1,2,3,4,5,6,
C．4,5,6,1,2,3,
D．6,5,4,3,2,1,