单项选择题

执行语句序列 ofstream outfile(“DATE.DAT”); if(…)cout<<"OK"; else cout<<"FAIL"后,如果文件打开成功,显示“OK”,否则显示"FAIL"。由此可知,上面if语句…处的表达式是:

A.outfilfail( )或outfile
B.outfilgood( )或outfile
C.outfilgood( )或!outfile
D.outfilfail( )或!out file