CT1 wroteNFHS:
If the ball is loose, there's no option: replay the down.
Snaqwells wroteThis is not true for NFHS. The team last in possession gets the option.
Replay the down or take the ball at the spot of the fumble.
If the IW occurs during a legal forward pass, legal kick or snap if flight, then there' no option: replay the down.
If the IW occurs during a fumble, backwards pass, illegal forward pass or illegal kick, the team last in possession has the option.
Both of these assume there's no accepted penalty.