First, a hint: The answer does not rely on any word play or the phrasing of the question. It’s just a really hard question that everybody knows the answer, but never thinks about. And so it’s hard to come up with. Here it is:
Name a mammal where if every one of them on the planet died today, there would still be more next year.
I’m quite certain that cats and dogs, and probably cows pigs and horses, among others, would also be correct- if every one of them somehow died today, there are enough eggs and sperm to make plenty more, and people definitely would. unfertilized Eggs and sperm should definitely not count as having to be included in the death of every one
A mule is the offspring of a male donkey and a female horse. If you killed off all mules today, there would still be male donkeys and female horses, therefore tomorrow (or sometime in the near future) there would be mules.
And where are you going to put those eggs and sperm once you fertilize them? in vitro fertilization is an amazing thing, but at some point you still gotta stick the fertilized cell(s) back into the animal.