<style>
    td {
        border: 1px solid black;
    }

    table {
        border-collapse: collapse;
    }
</style>
<table width="100%">
    <tbody>
        <tr>
            <td>
                A
            </td>
            <td>
                B
            </td>
            <td>
                C D
            </td>
        </tr>
    </tbody>
</table>