@deedee Nice catch! 
I think you’re referring to item 6 of the Get Set for Our Responsive Web Design Projects challenge:
Click the gear in the upper left hand corner of the CSS box, then copy this link https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css inside the text box. Now give your h1 element the class of text-primary to change its color and prove that Bootstrap is now available. Note that by using the dropdown menu and selecting “Bootstrap”, the Alpha v.4 will be added instead.
I’m pretty sure this needs to be changed since in the beta curriculum, bootstrap hasn’t been covered up to this point.
I’d chalk this one up to an error/bug that needs to be fixed, or at the least, clarified. If you want to file an issue about this so someone can fix or change it, go here: How to Report a Bug to the freeCodeCamp open source community. Let me know in a private message if you’d like help with this. 
For the tribute page project, I don’t think one will need to use too much (if any) Bootstrap, CSS Flexbox, or CSS Grid in order to pass the tests. This project is basically to get people used to the basic interactions between HTML and CSS.