I couldn't see the answer to this question, and so I guessed "C" which happened to be correct.

However, when I tried the three options on my system, "C" returned an error, "B" also returned an error, and "A" returned NULL.

I suspect that my errors had a similar cause to that reported by others. This leads me to make a suggestion for consideration by the adjudicators (if there are any!):

I suggest that before allowing a question to be used, the submitter must ensure that all assumptions and pre-conditions for the question be stated clearly. These assumptions would include such items as database names, table existence, as well as any security or user-privilege features necessary to ensure that the correct response would be produced when the query or procedure is run.

I have noted many instances of reports in this forum when queries have failed (and have had some such myself), and I feel that this shows poor appreciation by the submitter that not every system resembles his own.

Happy New Year to one and all!

Ken.