the question implies that all options guarantee promotion, so it'd be much sweeter and memorable to win the league from a last minute goal on the last day rather than having it guaranteed before the last game. We've already experienced that with Walsall.
C would be great, if we were hitting a late run to scrape into the playoffs, but having led the way all season it would be careless to have to do it that way, so I'd prefer A.
A but I've got to say C would be very sweet. We would think that our chance is gone on form, and come back from the dead if we won play offs