I would use a checkbox instead so you can just use a label if you want to link to it:



<!-- begin snippet: js hide: false console: true babel: false -->

<!-- language: lang-css -->

    .spoilerbutton {
      display: none;
    }

    .spoiler {
      overflow: hidden;
      height:2em;
    }

    .spoiler>div {
      -webkit-transition: all 0s ease;
      -moz-transition: margin 0s ease;
      -o-transition: all 0s ease;
      transition: margin 0s ease;
    }

    .spoilerbutton+.spoiler>div {
      margin-top: -500%;
    }
    .spoilerbutton+.spoiler>label:before {
      content: 'Antwoord';
      font-size: 150%;
      font-weight: bold;
      color: #000000;
    }
    .spoilerbutton:checked+.spoiler>label:before {
      content: 'Verberg';
    }

    .spoilerbutton:checked+.spoiler {
      height:auto;
    }
    .spoilerbutton:checked+.spoiler>div {
      margin-top: 0;
    }

<!-- language: lang-html -->

    <strong>1. Question 1?</strong> <input type="checkbox" id="question1" value="checked" class="spoilerbutton">
    <div class="spoiler">
      <label for="question1"></label>
      <div>
        <ul>
          <li><a href="#question2"><label for="question2">Open 2.</label></a></li>
          <li>possible answer 2.</li>
          <li>possible answer 3.</li>
        </ul>
      </div>
    </div>
    <strong>2. Question 2?</strong> <input type="checkbox" id="question2" value="checked" class="spoilerbutton">
    <div class="spoiler">
      <label for="question2"></label>
      <div>
        <ul>
          <li>possible answer 1.</li>
          <li>possible answer 2.</li>
          <li>possible answer 3.</li>
        </ul>
      </div>
    </div>

<!-- end snippet -->