Can some one explain why do I have to chose .container here as well, why is .jumbotron not enough? And why are some div-classes have div-containers (such as nav and jumbotron) but the div-class "learn-more" does not have a div-container?
Make a new CSS rule that selects the
<div class="container">..</div> inside
<div class="jumbotron">..</div>. Check out the example above.