<link href="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/css/bootstrap.min.css" rel="stylesheet" id="bootstrap-css">
<script src="//maxcdn.bootstrapcdn.com/bootstrap/4.1.1/js/bootstrap.min.js"></script>
<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<!------ Include the above in your HEAD tag ---------->
<label for="chkPassport">
<input type="checkbox" id="chkPassport" />
Do you have Passport?
</label>
<hr />
<div id="dvPassport" style="display: none">
Passport Number:
<input type="text" id="txtPassportNumber" />
</div>