comparison of correctness in multiple choice.
Multiple choice code is scattered and sometimes sends a list of
choices for the value, and sometimes a single string. We used to use
"in" which scarily handled both cases (list or substring search),
but that caused a bug when you had two choices like choice_1 and
choice10. Moving to == caused us to break when lists were sent to
us. So this ugly code is extra paranoid and checks both possibilities.
This really needs a better cleanup.
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