Hello m stuck on 45

stuck on 45 how to add an attribute with the value

  **Your code so far**
<html>
<body>
  <h1>CatPhotoApp</h1>
  <main>
    <section>
      <h2>Cat Photos</h2>
      <!-- TODO: Add link to cat photos -->
      <p>Click here to view more <a target="_blank" href="https://freecatphotoapp.com">cat photos</a>.</p>
      <a href="https://freecatphotoapp.com"><img src="https://cdn.freecodecamp.org/curriculum/cat-photo-app/relaxing-cat.jpg" alt="A cute orange cat lying on its back."></a>
    </section>
    <section>
      <h2>Cat Lists</h2>
      <h3>Things cats love:</h3>
      <ul>
        <li>cat nip</li>
        <li>laser pointers</li>
        <li>lasagna</li>
      </ul>
      <figure>
        <img src="https://cdn.freecodecamp.org/curriculum/cat-photo-app/lasagna.jpg" alt="A slice of lasagna on a plate.">
        <figcaption>Cats <em>love</em> lasagna.</figcaption>  
      </figure>
      <h3>Top 3 things cats hate:</h3>
      <ol>
        <li>flea treatment</li>
        <li>thunder</li>
        <li>other cats</li>
      </ol>
      <figure>
        <img src="https://cdn.freecodecamp.org/curriculum/cat-photo-app/cats.jpg" alt="Five cats looking around a field.">
        <figcaption>Cats <strong>hate</strong> other cats.</figcaption>  
      </figure>
    </section>
    <section>
      <h2>Cat Form</h2>
      <form action="https://freecatphotoapp.com/submit-cat-photo">
        <label><input type="radio">Indoor</label>
        <input type="text" name="catphotourl" placeholder="cat photo URL" required>
        <button type="submit">Submit</button>
      </form>
    </section>
  </main>
</body>
</html>
  **Your browser information:**

User Agent is: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_13_6) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/13.1.2 Safari/605.1.15

Challenge: Step 45

Link to the challenge:

Do you know what attribute your are supposed to add? If so, what value are you supposed to assign to the attribute? Where have you see attributes and values added in other elements in previous steps?