You can, but it isn't recommended by either HubPages or AC. HubPages would mark it as "duplicate content", which can lower your score; and AC will not pay you for it. Generally, it is said the the same article in more than one place will "compete with itself".
Having said that, some people may have their own reasons for wanting to post one article on more than one site. As long as you know the disadvantages there is no rule that says you can't do it.