Inline images are inserted into the output document using the image macro.

image:<target>[<attributes>]

The contents of the image file <target> is displayed.

	It was not the case in Bootstrap 2. So this attribute is useless for this version.

image::screenshots/bs2default-navbar-default-jumbotron-toc2.png[options="responsive"]

Renders:

Try several resolution and see what happens with or without responsive option.