<div class="form-group" >
<label for="inputCNAE">Atividade Primária</label>
  <br/>
 <select  class="browser-default custom-select">
 <?php
 $sql = mysqli_query($conn, "SELECT id_qualificacao_socio, descricao FROM Qualificacao_socio") or die(mysqli_error($conn));
  while($aux = mysqli_fetch_assoc($sql)) {
 ?>
 <option name ="id_qualificacao_socio" value='<?php echo $aux["id_qualificacao_socio"]?>'><?php echo $aux["descricao"] ?>
  </option>
  <?php
  }
   ?>
    </select>
</div>
<button type="submit" class="btn btn-primary">Enviar</button>