…c. This is one of those rare occasions. Both Apple’s and Google’s guidelines encourage designers to use tab bars (bottom navigations) consistently on every screen of the application:
One could argue that there are exemptions to this restrictive use of modality, e.g. for fullscreen detail-views like a single photo. Hiding the app’s overall UI (like tab bar) creates focus and minimises distraction. In this case, …
As soon as a user navigates from a top-level view to a child-view (eg. article) the child-view overlays the entire screen including the tab bar.