opción html deshabilitada
<label for="cars">Choose a car:</label>
<select name="cars" id="cars">
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="n/a" disabled>unavailable</option>
</select>
<select name="color" id="color">
<option value="" selected disabled hidden>Choose color...</option>
<option value="R">Red</option>
<option value="B">Blue</option>
</select>
VasteMonde