[greymule]

You're right, Buck. I omitted that the coach gets his choice only if the batter and all runners do not advance at least one base. I figured that with interference, that would have to be the case, but of course it might not be: they could all advance and then somebody interferes. Anyway, if they do advance a base, the catcher's obstruction is off.

I should heed my own advice about writing unambiguously!