def marked?(question, choice)
      return if not_registered
      marked_choices[question].find {|x| x==choice} ? true : false
    end
def marked?(question, choice)
      return if not_registered
      marked_choices[question].find {|x| x==choice} ? true : false
    end
True if the specified question/choice cell has been marked

 @param question [Integer] the question number, zero-based
 @param choice [Integer] the choice number, zero-based
 @return [Boolean]