NFHS Question 4 of week three

[zebra5150]

ok guys here is one more for this week Thanks again for all your help....

1st and goal from the B 9 yd. line. B12, part of B’s goal line defense, comes onto the field late. (a) B11, the player he is replacing, realizes he won’t be able to get off the field in time, so he leaves through end zone prior to the snap, or (b) B11 is running toward his sideline, but the ball is snapped before he is off the field, or (c) B11 goes off the field, but B12 enters the field just after the snap. He takes no action during the play. What, if any, fouls have occurred and how are they enforced?