mdb is not defined

Expected behavior I want to include selects html into row in a table Actual behavior The select don't work

Resources (screenshots, code snippets etc.)

 <div class="datatable">
                    <table>
                        <thead>
                            <tr>
                                <th class="th-sm">Ren</th>
                                <th class="th-sm">Cuenta</th>
                                <th class="th-sm">Nombre</th>
                                <th class="th-sm">Debe</th>
                                <th class="th-sm">Haber</th>
                                <th class="th-sm">Referencia</th>
                                <th class="th-sm">CC.</th>
                                <th class="th-sm">Concepto</th>
                                <th class="th-sm">Toc</th>
                            </tr>
                        </thead>
                        <tbody>
                            <tr>
                                <td>
                                    <div class="form-outline">
                                        <input type="text" id="form12" class="form-control" />
                                        <label class="form-label" for="form12">Example label</label>
                                    </div>
                                </td>
                                <td><select class="select">
<option value="1">One</option>
<option value="2">Two</option>
<option value="3">Three</option>
<option value="4">Four</option>
<option value="5">Five</option>
<option value="6">Six</option>
<option value="7">Seven</option>
<option value="8">Eight</option>

                                </td>
                                <td>Edinburgh</td>
                                <td>61</td>
                                <td>2011/04/25</td>
                                <td>$320,800</td>
                            </tr>

                        </tbody>
                    </table>
                </div>