Toby White (11/2/2009)
Even though A is empty string versus Null the answer is still obvious given that it is multiple choice. In other words it was obvious that the author had just made a mistake between empty/null since options A and C were so far off.
Except that A is not so far off. I thought along this line: this first select returns the empty string, I don't know what the second one does, but no answer has "this first select returns the empty string", so the only compatible answer is A: error.
Not nice.