#box_a1{
    width: 50%;
    height: auto;
    background-color: rgb(194, 194, 194);

    margin-left: 25%;
    border-radius: 20px;
    padding: 20px;
    margin-bottom: 10px;
}

#box_a1 img{
    width: 50%;
    margin-left: 25%;
    border-radius: 7px;
}

/* 当屏幕宽度小于   px时 */
@media (max-width: 700px) {
  #box_a1{
width: 90%;
margin-left: 5%;
margin-top: 30px;
  }

  #box_a1 img{
    width: 100%;
    margin-left: 0;
  }



}