Inline select with bootstrap
<select class="selectpicker" multiple data-max-options="2">
<option>Mustard</option>
<option>Ketchup</option>
<option>Relish</option>
</select>
<select class="selectpicker" multiple>
<optgroup label="Condiments" data-max-options="2">
<option>Mustard</option>
<option>Ketchup</option>
<option>Relish</option>
</optgroup>
<optgroup label="Breads" data-max-options="2">
<option>Plain</option>
<option>Steamed</option>
<option>Toasted</option>
</optgroup>
</select>