单项选择题

有以下程序:
#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);
fdose(fp);
printf("%d\n",n);

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