how can i read from a Label, or option selection and verify if it is exists or not

How can i read trough the HTML site and verify if for example M is there or not`?

<strong>Size:</strong>
	
																		 <select name="spec_116" onchange="changePrice()">
													 <option label="M" value="733391">M </option>
													 <option label="L" value="733392">L </option>
												 </select>	
							 <input type="hidden" name="spec_list" value="1" />
															 </dd>
	 </li>
			 <li class="clearfix">
	 <dd>

i have tried StringInStr, but that does not seem to work i am afraid