Some advice on answering a PL/SQL Challenge quiz

I received this email from a PL/SQL Challenge player recently:

"In the quiz for 11/06/2010, there was a question to identify the schame-level program or packaged subprogram provided by Oracle that can be used to identify if a file exists or not.

"In that, there was one of the options was FILE_EXISTS. As we've packaged subprogram webutil_file.file_exists, I was not sure whether to choose this option or not because of below reasons:

"1) if I don't choose file exists then it may be that you expect us to choose file_exists also (as there is a packaged subprogram named file_exists)

"2) If I choose file exists then it may be that you were expecting that we choose only webutil_file.file_exists should be choosen and not file_exists alone

"So in this way I was not sure whether file_exists alone was a correct choice to choose or not. Please help me understanding your views for this confusion."

In the case of this quiz, three of the four choices offered were of the form "UTL_FILE." and one was simply "FILE_EXISTS". It seems to us that the only reasonable conclusion to draw is that this reference to "FILE_EXISTS" without a package name could only mean a schema-level program, and not any subprogram with that name in any supplied package from Oracle. 

More generally, we recommend that you interpret the quiz question and choices as literally as possible. Do not make assumptions (beyond those we show you before you take the quiz). That puts the burden on us to provide quizzes without any ambiguity - which turns out to be harder than we thought it would be. But we believe we are getting better at it.