<div class="container-fluid">
<div class="row">
<div class="col-md-3 col-sm-6" style="background-color: palegreen;">.col-md-3 .col-sm-6</div>
<div class="col-lg-12 col-md-3 col-sm-6">.col-lg-12 .col-md-3 .col-sm-6</div>
<div class="col-md-3 col-sm-6" style="background-color: palegreen;">.col-md-3 .col-sm-6</div>
<div class="col-md-3 col-sm-6">.col-md-3 .col-sm-6</div>
<div class="col-md-3 col-sm-6" style="background-color: palegreen;">.col-md-3 .col-sm-6</div>
<div class="col-md-3 col-sm-6">.col-md-3 .col-sm-6</div>
</div>
</div>
xs~576(미만,px)/sm 576~768/md 768~992/lg 992~1200/xl 1200~1400/xxl 1400~
<!-- Force next columns to break to new line at md breakpoint and up -->
<div class="w-100 d-none d-md-block"></div>