CODE EXAMPLE FOR CSS

how to make the select box font size small in css

optgroup { font-size:40px; }
<select>
  <optgroup>
    <option selected="selected" class="service-small">Service area?</option>
    <option class="service-small">Volunteering</option>
    <option class="service-small">Partnership & Support</option>
    <option class="service-small">Business Services</option>
  </optgroup>
</select>