How about this one, then?

[Robert Goodman]

The more interesting question here is not the type of foul but when the ball is declared dead. We had at least one thread on here where one or more posters' answer was that the play is whistled dead as soon as you realize what's gone on (i.e. after the ball becomes live but before the down's normal termination), but that the foul is one deemed to occur as the ball was put in play, and the ball is retroactively ruled not to have been put in play.

So, just to liven things up, what if there's no such whistle and instead of a touchdown, A88 goes downfield a little and is interfered with by B21 attempting to catch the pass? (And the cool thing is, we still haven't specified whose code the game's played under, and it's an interesting question regardless. For Canadian football, assume the wing officials had "put up the gates".)