单项选择题

以下程序运行后的输出结果是
#include<stdio.h>
main( )
FILE * fp;int a[10]=1,2,3,i,n;
fp=fopen("d1.dat","w");
for(i=0;i<3;i++) fprintf(fp,"%d",a[i]);
fprintf(fp,"\n");
fclose(fp);
fp=fopen("d1.dat","r");
fscanf(fp,"%d",&n);
fclose(fp);
printf("%d\n",n);

A.12300
B.123
C.1
D.321