怎样让Table显示边框

<table summary="学生名单，包括学生编号、姓名、联系电话、和地址。"> 

    <caption>学生名单</caption> 

    <thead> 

        <th scope="col">编号</th> 

        <th scope="col">姓名</th> 

        <th scope="col">联系电话</th> 

        <th scope="col">地址</th> 

    </thead> 

    <tfoot> 

        <td colspan="4">班主任：</td> 

    </tfoot> 

    <tbody> 

        <tr> 

            <td>1</td> 

            <td>Jamson</td> 

            <td>123-45678</td> 

            <td>XX市XX区XX号</td> 

        </tr> 

        <tr> 

            <td>2</td> 

            <td>Grace</td> 

            <td>123-45678</td> 

            <td>XX市XX区XX号</td> 

        </tr> 

        <tr> 

            <td>3</td> 

            <td>Dizzy</td> 

            <td>123-45678</td> 

            <td>XX市XX区XX号</td> 

        </tr> 

    </tbody> 

</table>