probably because there is no explanation (note that correct answers with correct justifications generally do not have explanations).
In the browser console, I get
react-dom.production.min.js:52 Uncaught TypeError: Cannot read property 'text' of undefined
at e.handleSubmitQuiz (QuizQuestion.jsx:97)
at Object.l (react-dom.production.min.js:14)
at p (react-dom.production.min.js:14)
at react-dom.production.min.js:14
at b (react-dom.production.min.js:15)
at it (react-dom.production.min.js:52)
at ot (react-dom.production.min.js:51)
at lt (react-dom.production.min.js:52)
at pt (react-dom.production.min.js:56)
at D (react-dom.production.min.js:287)
probably because there is no explanation (note that correct answers with correct justifications generally do not have explanations). In the browser console, I get