如果d盘上的A.txt文件的内容有如下两行: CB1+2=3D ZX7*8!! 则下列程序运行后D盘上的B.txt文件的内容为______ #include <stdio.h> #include <stdlib.h> int main( ) { int c; FILE *fp1,*fp2; if((fp1=fopen("D:\\A.txt","r"))==NULL) { printf("file error!\n"); exit(0); } if((fp2=fopen("D:\\B.txt","w"))==NULL) { printf("file error!\n"); exit(0); } c=fgetc(fp1); while(c!=EOF) { if (c>='0' && c<='9') fputc(c,fp2); c="fgetc(fp1);" } fclose(fp1); fclose(fp2); return 0;>