<input type="radio" name="brower"> 必须一起存在，不然单选框有误。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>Document</title>
<script>
function F(x)
{
document.getElementById("answer").value=x;
}
</script>
</head>
<body>
<p>您最喜欢哪款浏览器</p>
<form>
<input type="radio" name="brower" onclick="F(this.value)" value="Internet Explorer">Internet Explorer <br>
<input type="radio" name="brower" onclick="F(this.value)" value="Firefox">Firefox <br>
<input type="radio" name="brower" onclick="F(this.value)" value="Netscape">Netscape <br>
<input type="radio" name="brower" onclick="F(this.value)" value="Opera">Opera <br>
您喜欢的浏览器是：<input type="text" id="answer" size="20">
</form>
</body>
</html>