有以下程序

#include <stdio.h>

main()

{ FILE *pf;

char *s1="China",*s2="Beijing";

pf=fopen("abc.dat","wb+");

fwrite(s2,7,1,pf);

rewind(pf);

fwrite(s1,5,1,pf);

fclose(pf);

}

以上程序执行后 abc.dat 文件的内容是

A)China

B)Chinang

C)ChinaBeijing

D)BeijingChina