(1) Well without more specialist knowledge, one could still reasonably conclude they are different species, B, if only because it is common knowledge !. Beyond that, I guess a lay person might know that interspecific breeding (between species) often yields problems with the F1 generation* This obviously eliminates A !

(2) A biologist (me) could despatch D, though the wording is terrible - natural selection produces results. If it is supposed to mean that natural selection would eventually stop interbreeding of F2 and subsequent generations - yes it would. More on why next...

(3) C requires specific acquaintance with the species involved and knowledge of their hybridising results. I had to look it up - male mules are also sterile most of the time, so it does not apply either. And so, in reference to this and (2) F2** and subsequent generations are never really going to be viable in broad terms as a wild population.

* &** an F1 generation (filial 1) is the offspring of the original parental species, the horse and donkey that yields the mule/hinny. An F2 generation would be the offspring of mating these with themselves.

They can rarely produce a fertile offspring. I think the best answer is they are different species within the same kind.

Horses and donkeys are able to mate and produce mules which develop normally but are not able to reproduce themselves because they are sterile what do you conclude about horses and donkeys

A. They are the same species

B. They are different species

C. Only females mules are sterile

D. Mules result In natural selection