In the weekly Unexpected Elements multiple-choice quiz, the answer is almost NEVER ‘a’. It’s nearly always ‘b’, or ‘c’. Why is this? When we set the quiz, why are we so reluctant to choose option ‘a’?

Use a No. 2 pencil, fill out each circle completely, and don't make any stray marks--these are rules every child learns when taking standardized tests that are largely based on multiple choice. But ...