有个练习题请大侠们帮忙
菜鸟在自学Javascript，这儿有个练习题，想请大侠们给我个答案-----------------------
<html>
<head>
<title>JavaScript Variables</title>
<script type="text/javascript">
//ADD PROMPT HERE
</script>
</head>
<body>
<form>
<input type="button" value="Paul"
onclick="alert('Paul');"/>
<br/><br/>
<input type="button" value="John"
onclick="alert('John');"/>
<br/><br/>
<input type="button" value="George"
onclick="alert('George');"/>
<br/><br/>
<input type="button" value="Ringo"
onclick="alert('Ringo');"/>
<br/><br/>
<!--ADD BUTTON HERE-->
</form>
</body>
</html>
