90% fail this challenge?
MATL, 16 14 bytes

-1 byte thanks to @Giuseppe

-1 byte thanks to @LuisMendo

SY'ts/i-|tX&lt;=)


Explanation:

        % implicit input
S       % sort
Y'      % run-length encoding
ts      % duplicate elements and sum (get number of elements)
/       % array right division (get array of probability for each answer)
i-|     % get absolute difference with second input
tX&lt;     % duplicate and get minimum value
=)      % get each answer that match with the minimum value
        % (implicit) convert to string and display


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