以下正确引入JS文件的是？
A在body标签外边的下边写入<script href="js/demo.js"></script>
B在body标签内写入<script src="js/demo.js"></script>
C在body标签外边的下边写入<script src="js/demo.js"></script>
D在body标签内写入<script href="js/demo.js"></script>
A在body标签外边的下边写入<script href="js/demo.js"></script>
B在body标签内写入<script src="js/demo.js"></script>
C在body标签外边的下边写入<script src="js/demo.js"></script>
D在body标签内写入<script href="js/demo.js"></script>