How to get rid out of this problem?

“Your code should add a box-shadow property for the thumbnail id.”

<style>

  h4 {

    text-align: center;

    background-color: rgba(45, 45, 45, 0.1);

    padding: 10px;

    font-size: 27px;

  }

  p {

    text-align: justify;

  }

  .links {

    text-align: left;

    color: black;

  }

  .color{

    box-shadow: 0 10px 20px rgba(0,0,0,0.19), 0 6px 6px rgba(0,0,0,0.23);

  }

   

  .fullCard {

    width: 245px;

    border: 1px solid #ccc;

    border-radius: 5px;

    margin: 10px 5px;

    padding: 4px;

  }

  .cardContent {

    padding: 10px;

  }

  .cardText {

    margin-bottom: 30px;

  }

</style>

<div class="fullCard" >

  <div class="cardContent">

    <div class="cardText">

      <div class="color" id="thumbnail"> </div>

        

      <h4>Alphabet</h4>

      <hr>

      <em><p>Google was founded by Larry Page and Sergey Brin while they were <u>Ph.D. students</u> at <strong>Stanford University</strong>.</p></em>

    </div>

    <div class="cardLinks">

      <a href="https://en.wikipedia.org/wiki/Larry_Page" target="_blank" class="links">Larry Page</a><br><br>

      <a href="https://en.wikipedia.org/wiki/Sergey_Brin" target="_blank" class="links">Sergey Brin</a>

    </div>

  </div>

</div>

you need to use that id to add that style

really appreciated

thanx for ur help