Alinhar formulário

Boa noite,

Estou montando um formulário de pesquisa numa página. Testando aqui em desktop o formulário fica ok, só que em mobile não fica com uma divisão legal, os 5 inputs e selects ficam em duas linhas.

html

<form id="pesquisar" method="post" action="resultado/">
 <div class="column-fifth">
 <input type="text" id="pesquisar_empresa" name="pesquisar_empresa" class="inputs" value="Pesquisar empresas" />
 </div><!-- column-fifth -->

 <div class="column-fifth">
 <select id="ramo" name="ramo" class="inputs">
 <option value="">Segmento</option>
 </select>
 </div><!-- column-fifth -->

 <div class="column-fifth">
 <select id="estado" name="estado" class="inputs">
 <option value="">Estado</option>
 </select>
 </div><!-- column-fifth -->

 <div class="column-fifth">
 <select id="cidade" name="cidade" class="inputs">
 <option value="0">Cidade (Selecione primeiro um estado)</option>
 </select>
 </div><!-- column-fifth -->

 <div class="column-fifth">
 <input type="submit" id="bt_pesquisar" value="Buscar" />
 </div><!-- column-fifth -->
</form>

css

#pesquisar {
 width: 100%;
 float: left;
}

#pesquisar .inputs {

 width: 100%; height: 25px;
 float: left;
 background: #f7f7f7;
 border: 1px solid #ccc;
}
#pesquisar_empresa {
 height: 22px !important;
}

#pesquisar #bt_pesquisar {

 background: #E07000;
 border: none;
 padding: 3px 5px 3px 5px;
 float: right;
 margin-right: 35%;
 color: #fff;
 cursor: pointer;
}

#pesquisar #bt_pesquisar:hover {

 background: #fff;
 color: #E07000;
}

grid

/**
* @section Grid
* Grid definitions here
*/

.cf:before, .cf:after { content: " "; display: table }
.cf:after { clear: both }

[class*="column-"] {

 -webkit-box-sizing: border-box;
 -moz-box-sizing: border-box;
 -ms-box-sizing: border-box;
 -o-box-sizing: border-box;
 box-sizing: border-box;
 *behavior: url('boxsizing.htc');
 float: left;
 padding-left: 15px;
 padding-right: 15px;
}

.column-full { max-width: 1170px; float: none; }
.column-eleven-twelfths { width: 91.6667%; }
.column-ten-twelfths { width: 83.3334%; }
.column-three-quarters { width: 75%; }
.column-two-thirds { width: 66.6667%; }
.column-three-fifths { width: 60%; }
.column-seven-twelfths { width: 58.3334%; }
.column-half { width: 50%; }
.column-five-twelfths { width: 41.6667%; }
.column-two-fifths { width: 40%; }
.column-third { width: 33.3333%; }
.column-quarter { width: 25%; }
.column-fifth { width: 20%; }
.column-sixth { width: 16.6667%; }
.column-twelfth { width: 8.3333%; }

.space-bottom-big { margin-bottom: 60px }
.space-bottom { margin-bottom: 40px }
.space-bottom-small { margin-bottom: 20px }

.fleft { float: left }
.fright { float: right }
.clear { clear: both }

[class*="column-"].content { float: none; max-width: 1170px; padding-left: 0; padding-right: 0; }

.content { margin-left: auto; margin-right: auto; float: none; }

.column-half .column-quarter { width: 50%; }
.column-three-quarters .column-quarter { width: 33.3333%; }

[class*="column-"].column-grid { padding-left: 0; padding-right: 0; }
/**
* @section Responsive
* Responsive rules on this file
*/
@media only screen and (max-width: 1170px) {
img { max-width: 100% !important; height: auto !important; }

.column-full { width: auto; }
.content { padding-left: 15px; padding-right: 15px; }
}
@media only screen and (max-width: 1024px) {
.space-bottom-big { margin-bottom: 40px }
}
@media only screen and (max-width: 1060px) {
[class*="column-"].content { width: 100%; }

.column-three-quarters { width: 100%; float: none; }

.column-half.content { width: 50%; }
}
@media only screen and (max-width: 960px) {
.column-half.content { width: 100%; }

 .column-quarter,
 .column-three-quarters .column-quarter { width: 50%; }

 .column-fifth { width: 25%; }
 .column-fifth.column-single { margin-left: auto; margin-right: auto; float: none; clear: both; }

 .column-twelfth { width: 16.6667%; }
}

@media only screen and (max-width: 660px) {
.column-third:nth-child(n) { clear: both; float: none; padding-left: 15px; padding-right: 15px; width: 100%; }

.column-fifth { width: 50%; }

.column-sixth { width: 33.3333%; }
.column-sixth:nth-child(3n+1) { clear: both; }

 .column-three-fifths,
 .column-two-fifths,
 .column-seven-twelfths,
 .column-five-twelfths { width: 100%; }

 .column-single { margin-left: auto; margin-right: auto; float: none; clear: both; }
}

@media only screen and (max-width: 480px) { .column-half:nth-child(n) { clear: both; float: none; padding-left: 15px; padding-right: 15px; width: 100%; }

.column-three-quarters .column-quarter,
.column-half .column-quarter,
.column-quarter { width: 100%; float: none; clear: both; }

.column-twelfth { width: 33.3333%; }

[class*="column-"].content { padding-left: 0; padding-right: 0; }
}
@media only screen and (max-width: 320px) {

}

Obrigado pela atenção.