JSFiddle - React, Tailwind, and code Playground

HTML

<select id="ref" name="selectbasic ix-select-how" class="input-xlarge">
<option value="" label=""></option>                                                  
<option value="SearchEngine" label="Suchmaschine">Suchmaschine</option>                                         
<option value="Webhostlist" label="Webhostlist">Webhostlist</option>                                            
<option value="Press" label="Presse">Presse</option>                                            
<option value="Friend" label="Bekannte">Bekannte</option>                                           
<option value="ByChance" label="Zufällig">Zufällig</option>                                         
<option value="Others" label="Sonstige">Sonstige</option>                                       
</select>
<div class="control-group ix-hidden"></div>

JavaScript

$('#ref').change(function () {
    if ($(this).val() === 'Others') {
        $("div.control-group.ix-hidden").append("<label class='control-label'>Wie?</label><div class='controls'><div class='input-prepend'><span class='add-on'><i class='icon-globe'></i></span><input type='text' class='input-xlarge' id='email' name='email' placeholder='Wie?'></div></div>");
    }
});