A.ifstreamfin;fin.open(“d:\test.txt”,ios_base::in);
B.fstmamfin;fin.open(“d:\test.txt”,ios_base::out);
C.ofstreamfout;fout.open(“d:\test.txt”,ios_base::out);
D.ofstreamfout;fout.open(“d:\test.txt”,ios_base::app);