Since I have found that most of today's students can't spell worth a damn, I tend to include terms that are very similar, but often aren't even real terms, as red herrings. Since there are more answers than questions, this would mean that I have empty questions with wrong answers interspersed. And sure enough, students always fall for these misspelled words.
Maybe I just need to keep the answer lists short enough to be completely visible within the screen, and hope too many students don't complain! Having answers in alphabetical order is just always the norm, so I'm not sure why Moodle has never realized that! It would annoy me if I were the one taking the test, so I can sympathize with students who want to see the answers in alphabetical order!