<div class="container-fluid">
  <div class="row flex-xl-nowrap">
    <div class="col-12">
      <div class="bd-example">
        <div id="carouselExampleCaptions" class="carousel slide" data-ride="carousel">
          <ol class="carousel-indicators">
            <li data-target="#carouselExampleCaptions" data-slide-to="0" class="active"></li>
            <li data-target="#carouselExampleCaptions" data-slide-to="1"></li>
            <li data-target="#carouselExampleCaptions" data-slide-to="2"></li>
            <li data-target="#carouselExampleCaptions" data-slide-to="3"></li>
          </ol>
          <div class="carousel-inner">
            <div class="carousel-item active">
              <div class="block4-wrap">
                <div class="block4"><img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=1" alt="First slide">
                  <div class="my-captions">
                    <h5>First slide label</h5>
                    <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
                  </div>
                </div>
                <div class="block4"><img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=1" alt="First slide">
                  <div class="my-captions">
                    <h5>First slide label</h5>
                    <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
                  </div>
                </div>
                <div class="block4"><img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=1" alt="First slide">
                  <div class="my-captions">
                    <h5>First slide label</h5>
                    <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
                  </div>
                </div>
                <div class="block4"><img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=1" alt="First slide">
                  <div class="my-captions">
                    <h5>First slide label</h5>
                    <p>Nulla vitae elit libero, a pharetra augue mollis interdum.</p>
                  </div>
                </div>
              </div>
            </div>
            <div class="carousel-item">
              <div class="block4-wrap">
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=2" alt="Second slide">
                  <div class="my-captions">
                    <h5>Second slide label</h5>
                    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=2" alt="Second slide">
                  <div class="my-captions">
                    <h5>Second slide label</h5>
                    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=2" alt="Second slide">
                  <div class="my-captions">
                    <h5>Second slide label</h5>
                    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=2" alt="Second slide">
                  <div class="my-captions">
                    <h5>Second slide label</h5>
                    <p>Lorem ipsum dolor sit amet, consectetur adipiscing elit.</p>
                  </div>
                </div>
              </div>
            </div>
            <div class="carousel-item">
              <div class="block4-wrap">
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=3" alt="Third slide">
                  <div class="my-captions">
                    <h5>Third slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=3" alt="Third slide">
                  <div class="my-captions">
                    <h5>Third slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=3" alt="Third slide">
                  <div class="my-captions">
                    <h5>Third slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=3" alt="Third slide">
                  <div class="my-captions">
                    <h5>Third slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
              </div>
            </div>
            <div class="carousel-item">
              <div class="block4-wrap">
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=4" alt="Fourth slide">
                  <div class="my-captions">
                    <h5>Fourth slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=4" alt="Fourth slide">
                  <div class="my-captions">
                    <h5>Fourth slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=4" alt="Fourth slide">
                  <div class="my-captions">
                    <h5>Fourth slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
                <div class="block4"> <img class="d-block w-100" src="http://placehold.it/500/bbb/fff&amp;text=4" alt="Fourth slide">
                  <div class="my-captions">
                    <h5>Fourth slide label</h5>
                    <p>Praesent commodo cursus magna, vel scelerisque nisl consectetur.</p>
                  </div>
                </div>
              </div>
            </div>
          </div>
          <a class="carousel-control-prev" href="#carouselExampleCaptions" role="button" data-slide="prev"> <span class="carousel-control-prev-icon" aria-hidden="true"></span> <span class="sr-only">Previous</span> </a> <a class="carousel-control-next" href="#carouselExampleCaptions" role="button" data-slide="next"> <span class="carousel-control-next-icon" aria-hidden="true"></span> <span class="sr-only">Next</span> </a> </div>
      </div>
    </div>
  </div>
</div>

.carousel-item img {
	margin:10px;
}
.block4-wrap {
	display:flex
}
.block4 {
	flex:1 0 25%;
	background:#000;
	color:#fff;
}
.my-captions{margin:10px;padding-bottom:3em}

/* fix width and make user scroll with mouse/touch to see the items */
@media screen and (max-width:768px){
	.block4{max-width:280px;flex:1 0 100%;overflow:hidden}	
	.carousel{overflow:hidden;}
	.carousel-inner{overflow-x:visible;}
}
@media screen and (max-width:480px){
	.block4{max-width:240px;}	
}