RioBRChess, yes in a normal game, whites first move on these puzzles are set up so that in general it's the only move that can be made then, black moves what do you do then, if black makes a weak move you play accordingly.
Yes, I see that, Bryan. Well, I say that, but it took you to point it out to me. It's a shame, I guess, that the problem didn't go further by simply illustrating it. Thanks for doing so; it's finally clear to me.