[bes]

<style>
  .hide {
    display: none;
  }
</style>

<select id="sel">
  <option>первый вариант</option>
  <option>второй вариант</option>
  <option>третий вариант</option>
</select>
 
<div id="div">
<select>
  <option>68</option>
  <option>74</option>
</select>
     
<select class="hide">
  <option>110</option>
  <option>116</option>
</select>

<select class="hide">
  <option>115</option>
  <option>119</option>
</select>

<script>
window.onload = function () {
  var sel = document.getElementById('sel');
  var div = document.getElementById('div');
  var curIndex = 0;

  sel.onchange = function () {
    div.children[curIndex].style.display = 'none';
    curIndex = sel.selectedIndex;
    div.children[curIndex].style.display = 'block';
  }

}
</script>