I'm seeing a bunch of you talking about saving the adult so you can both save the children, and it's getting kind of annoying >.<
The situation is irrelevant to what he's asking. The question at hand is asking about your morals, not the logical thing to do in that situation (Call 911, try to catch kid + baby because they're lighter etc etc) it's about if you were in the situation in which you had 3 people in front of you who were about to die REGARDLESS OF HOW and you had the opportunity to save one of them, (baby, child, adult) who'd it be?
I'll restate my answer just to stay on topic. I'd choose the baby. Killing the baby would be heartless, those of you saying "think of it as a late abortion" I think the parents would think differently >.>.. I couldn't go through killing another person who doesn't even have a say in if they live or not, I'd be robbing them of their life. Yes, you could say that about the child and adult. But they've experienced the world, and depending on how they interpret their near-death experience, they could potentially become depressed/insane. Meanwhile the baby who hasn't developed a sense of memory or awareness would go through his life being unaffected by that event. Of course there are multiple things that could go wrong with my theory, but regardless.
Oh, and another thing. Someone (forgot who) mentioned morals being an illusion of lower intelligence. You couldn't decipher a whole persons intelligence in a split second just by looking at them, that's impossible. If you believe otherwise, you're ignorant.