2. In animals, I think, it can sometimes be 1, because the cord attaches to a sac (which two fetuses could theoretically share) rather than directly to the baby. I may have made that up, but I THINK that's true.
In humans, though, I DO know, and the answer is that each baby has its own cord. Interestingly, there CAN be (but don't have to be) 2 placentas.