string(a)

src/Quiz.js

@@ -53,7 +53,7 @@ function Quiz() {
                         <form>
                             {question.Choose.map((a, index) =>
                                 <div>
-                                    <input type="radio" name='answer' id={index} value={a} onChange={handleChange} checked={parseInt(selected) === a} />
+                                    <input type="radio" name='answer' id={index} value={a} onChange={handleChange} checked={selected === String(a)} />
                                     <label className="font-weight-bold" htmlFor={a}>{a}</label>
                                 </div>
                             )}