It's a stupid, loaded question.
If I have to choose between saving my mother or my grandmother that doesn't mean the other one is less human.
Choosing between 1000 of anything and one of something is just as loaded. it's done to make saving the unborn seem less practical and the five yr old therefore seems a better choice.
Refering to the unborn as embryos is also loaded. this is done to dehumanize the unborn and again make the 5yr old seem like a more practical choice