If a Mastodon Dies While Walking Along a River,what Needs

If a mastodon dies while walking along a river,what needs to happen in order to fossilize the body?

A) A drought must occur so the body can be dried out.
B) A flood must occur so that sediment can wash over the body.
C) No changes are necessary; it will be preserved just by being near a river.
D) The body must be carried away by scavengers to another location.