Once the user has picked all possible answers from a multiple answer question, the non-selected answers don't get disabled. Unlike when the question type is single.
This can be observed in question four of the demo provided (https://wingkwong.github.io/react-quiz-component)
Non-selected answers is being greyed out as expected (question type: single)

Non-selected answer isn't being greyed out (question type: multiple)

This issue allows the user to keep selecting answers even after they've selected as many answers as they are allowed, causing this in the the results page
