Imagine That You and Charles Darwin Are Looking at a Newborn

Imagine that you and Charles Darwin are looking at a newborn litter of kittens,and the kittens are all a bit different from one another.As you observe the kittens,you ask Mr.Darwin which of the kittens will be most "fit" in terms of natural selection.What would Mr.Darwin be most likely to say in response to your question

A)  "The one who has the most kittens of its own." 
B)  "Because they are related and carry the same genes, they all have equal fitness." 
C)  "The one that is the strongest and the most aggressive." 
D)  "The one that requires the smallest amount of resources."