how to add hover for Aboutus

<li class="has-mega-menu"><a href="@Url.RouteUrl("Topic", new {SeName = Html.GetTopicSeName("aboutus") })">ABOUTUS</a>

    <div class="top-menu-triangle"></div>
  <div class="mega-menu">
      <div class="row">
          <div class="col-xs-4 col-md-4 "  >
              <div class="img-holder">
                  <img style="width:50%;height:50%;float:left" src="../../Content/images/who.png" >
                  <ul style="float:left;margin-top:5px;text-align:left">
                      <li style="list-style:none;color:#757b81">MicroAnalytix is an Australian owned laboratory supply company which was established in 1988. Since then, the organisation has grown to providing laboratory products ...<a href="about-us" style="text-decoration:underline">Learn more</a></li>
                  </ul>
                 </a>
              </div>

          </div>
          <div class="col-xs-4 col-md-4">
              <div class="img-holder">
                  <img style="width:50%;height:50%;float:left" src="../../Content/images/what.png" >
                  <ul style="float:left;margin-top:5px;text-align:left ">
                      <li style="list-style:none;color:#757b81">We have purpose built offices in Melbourne, Queensland with our head office and warehouse located in Sydney. Auckland, in New Zealand's North Island is our NZ head office ...<a href="about-us" style="text-decoration:underline">Learn more</a></li>

                  </ul>
                 </a>
              </div>
          </div>
          <div class="col-xs-4 col-md-4" >
              <div class="img-holder">
                  <img style="width:50%;height:50%;float:left" src="../../Content/images/about.png" >
                  <ul style="float:left;margin-top:5px;text-align:left">
                      <li style="list-style:none;color:#757b81">More recently, Microanalytix has been focusing on the introduction of new product lines and have become sort after technical advisors on numerous applications and products...<a href="about-us" style="text-decoration:underline">Learn more</a></li>

                  </ul>
                 </a>
              </div>

      </div>
  </div>