Your page source clearly shows that the text is there.
Code:
<li><label for="rb_optionnumber_1"><input type="radio" name="optionnumber" value="1" id="rb_optionnumber_1" tabindex="1" /> Yes</label></li>
<li><label for="rb_optionnumber_2"><input type="radio" name="optionnumber" value="2" id="rb_optionnumber_2" tabindex="1" /> No</label></li>
You either have some css that is setting the display to none or your text is the same color as the background.