Both a stack and a queue store items and hand them back one at a time. Why does reversing which end you remove from make one of them right for undo history and the other right for a print spooler?

C. Because the removal order encodes a different relationship to time.

The two differ in one decision, which end you remove from, and that decision encodes a policy about time. Last-in-first-out returns the most recent, which is precisely what undo means. Using a stack for a spooler would serve the newest job first, leaving a nine a.m. document unprinted all day. The choice is never about speed; both are constant time.