单项选择题

执行语句序列
ofstream outfile("DATA.DAT");
if(...)cout<<"OK";else cout<<"FAIL";
后,如果文件打开成功显示"OK",否则就显示"FAIL"。由此可知,上面if语句的…处的表达式应是

A.outfile.fail()或outfile
B.outfile.good()或!outfile
C.outfile.good()或outfile
D.outfile.fail()或!outfile