How is this not D?!

Hi Tyler808, This question is asking us what must be true in order for counting sheep to be effective. D tells us that we would automatically fall asleep when we think about sheep. This is insane. If D were true, one will fall asleep if they drive past a sheep. A vet working on a sheep would fall asleep while working, and a shepard would never be awake. It does not have to be true that thinking of sheep always guarantees sleep- in fact, the argument is only about counting sheep, a very specific subset of thinking about sheep.