文章の下線の長さについて

ご質問失礼します。
下線の長さをいっぱいに伸ばしたいのですが、ご教示いただければ幸いです。

PHP
1<section id="news" class="news">
2				<div class="container">
3					<div class="section-header">
4						<h2><img class="img-fluid news-img" src="<?php echo get_template_directory_uri(); ?>/images/title-news.png"	alt="title-news"></h2>
5					</div>
6					<hr class="lines">
7					<div class="row">
8						<?php get_template_part( 'template-parts/content', 'news' ); ?>
9						<a class="twitter-timeline" width="600px" height="300px" href="https://twitter.com/only4106?ref_src=twsrc%5Etfw">Tweets by only4106</a> <script async src="https://platform.twitter.com/widgets.js" charset="utf-8"></script>
10					</div>
11				</div>
12			</section><!-- .news -->

SCSS
1/*--------------------------------------------------------------
2# news
3--------------------------------------------------------------*/
4.news {
5	position: relative;
6	padding: 20rem 0 70rem 0;
7	background:
8	url(images/illust-news01.png)	90%	60%	no-repeat,
9	url(images/illust-access02.png)	5%	0%	no-repeat,
10	url(images/bg-news.png)	center	top /cover	no-repeat;
11}
12
13.news .news-img {
14	display: block;
15	margin: 0 auto;
16}
17
18.news .lines {
19	border-top: .1rem solid $white;
20}
21
22.news ul {
23	list-style: none;
24	color: $white;
25	@include media-breakpoint-down(sm) {
26		margin-bottom: 3rem;
27	}
28}
29ul li {
30	width: 100%;
31	border-bottom: 1px solid $white;
32}
33
34.news .twitter-timeline {
35	position: absolute !important;
36	top: 74rem;
37	left: 40rem;
38	@include media-breakpoint-down(sm) {
39			position: relative !important;
40			top: 0;
41			left: 0;
42	}
43}
44
45.entry-date {
46	margin-bottom: 0;
47	@include media-breakpoint-down(sm) {
48		display: block;
49		margin-bottom: .5rem;
50	}
51}
52
53.news .entry-title {
54	display: inline-block;
55	font-size: 1rem;
56	@include media-breakpoint-down(sm) {
57		display: block;
58	}
59}

完成しました、ありがとうございます。

PHP
1<ul class="scroll-list">
2		<?php
3		$args = array( 'posts_per_page' => 4 );
4
5		$myposts = get_posts( $args );
6		foreach ( $myposts as $post ) : setup_postdata( $post ); ?>
7
8		<li class="scroll-item">
9			<time class="entry-date" itemprop="datePublished" datetime="<?php the_modified_date('c') ?>"><?php echo get_the_date( 'Y/m/d' ); ?></time>
10			<h3 class="entry-title"><?php the_title(); ?></h3>
11		</li>
12
13		<?php endforeach;
14		wp_reset_postdata();?>
15	</ul>

SCSS
1/*--------------------------------------------------------------
2# news
3--------------------------------------------------------------*/
4.news {
5	position: relative;
6	padding: 20rem 0 70rem 0;
7	background:
8	url(images/illust-news01.png)	90%	60%	no-repeat,
9	url(images/illust-access02.png)	5%	0%	no-repeat,
10	url(images/bg-news.png)	center	top /cover	no-repeat;
11}
12
13.news .news-img {
14	display: block;
15	margin: 0 auto;
16}
17
18.news .lines {
19	margin: 0;
20	border-top: .1rem solid $white;
21}
22
23.news .scroll-list {
24	list-style: none;
25	padding: 0;
26	color: $white;
27	@include media-breakpoint-down(sm) {
28		margin-bottom: 3rem;
29	}
30}
31.news .scroll-item {
32	border-bottom: .1rem dotted $white;
33}
34
35.news .twitter-timeline {
36	position: absolute !important;
37	top: 74rem;
38	left: 40rem;
39	@include media-breakpoint-down(sm) {
40			position: relative !important;
41			top: 0;
42			left: 0;
43	}
44}
45
46.entry-date {
47	display: inline-block;
48	padding: 1rem 1rem;
49	@include media-breakpoint-down(sm) {
50
51	}
52}
53
54.news .entry-title {
55	display: inline-block;
56	font-size: 1rem;
57	@include media-breakpoint-down(sm) {
58	}
59}