.one{
     width: 380px; 
    height: 285px;
    
     margin:0 auto;
      align:center;
    position:relative;
    transition:all 2s;
     background:url("https://www.nuit.edu.cn/Content/wxzx/Base/img/BigBackgroud2.jpg") no-repeat center;

 }
.two{
   width: 380px;
    height: 285px;
   align:center;
    margin:0 auto;
    position:relative;
   
    transition:all 2s;
    background:url("https://www.nuit.edu.cn/Content/wxzx/Base/img/BigBackgroud3.jpg") no-repeat center;

}