let sentence = $('.sentence').text();

sentences = sentence.split('.')
$('.sentence').html('');

for (let s of sentences) {
  $('.sentence').append('<span>' + s + '.</span>')
}

$('.sentence span').on('click', function() {
  $(this).addClass('highlight').siblings().removeClass('highlight');
});

 .sentence span:hover,
.highlight {
  background: Yellow;
}

 window.smoothScroll = function (target) {
            var scrollContainer = target;
            do { //find scroll container
                scrollContainer = scrollContainer.parentNode;
                if (!scrollContainer) return;
                scrollContainer.scrollTop += 1;
            } while (scrollContainer.scrollTop == 0);

            var targetY = 0;
            do { //find the top of target relatively to the container
                if (target == scrollContainer) break;
                targetY += target.offsetTop;
            } while (target = target.offsetParent);

            scroll = function (c, a, b, i) {
                i++;
                if (i > 30) return;
                c.scrollTop = a + (b - a) / 30 * i;
                setTimeout(function () {
                    scroll(c, a, b, i);
                }, 20);
            }
            // start scrolling
            scroll(scrollContainer, scrollContainer.scrollTop, targetY, 0);

        }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<p class="sentence">
(1)Lorem ipsum dolor sit amet consectetur adipiscing elit.
(2)Pellentesque iaculis.
(3)Pellentesque iaculis nisl at erat dapibus cursus.
(4)Pellentesque iaculis.
(5)amet consectetur adipiscing elit.
(6)adipiscing elit.
</p>