Aristotle said that a moving earthly or 'mundane' object with nothing pushing or pulling on it will always A slow down and stop. B speed up. C keep moving at the same speed. D follow a circular path.

A slow down and stop

Explanation:

When there is no force acting on something it automatically begins to slow down and then stops. Essentially, Aristotle's perspective of motion is that "it requires a force to move an object in an unnatural" way - or, plainly, that "movement involves strength." Indeed, if you propel a book, it keeps moving. Once you stop trying to push, it comes to a stop.