I am currently in the process of redesigning a job advert site and am trying to put a lot more effort into my SEO.

My question is how should I deal with the URLs that point to job adverts when the advert expires. The options I have thought of so far are:

1. Return a 404 error and redirect to a 404 page. Will it have an effect on ranking if there are a lot of URLs that return 404s after only being up for a few weeks?
2. Redirect to job listing page - When the user requests a URL for an advert that has expired just redirect to the main job listing page.
3. Show the advert but tell the user to has closed - Show the advert page but with a notification that the advert has closed. The issue I see with this is that the user will visit the page, see its closed and then leave the site again which would not be good for rankings