What is the purpose of the event window.onpopstate?

Answer: Option C

The window.onpopstate event is fired whenever a state object is removed from the browser history, which occurs on browser “back” or “forward”. State objects are persisted on the user’s hard disk between sessions, which is a nice feature. The object passed into a call to pushState or replaceState is provided as the state property on the event object in the “popstate” event.