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); fclose(fp); printf("%d\n",n); } 程序的运行结果是

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