What level is a group of organism that is so similar it can breed offspring

Question- What level is a group of organism that is so similar that it can breed offspring?

Answer- A species is a group of similar organisms that can breed with one another to produce fertile offspring. According to this definition, one species is distinguished from another when, in nature, it is not possible for matings between individuals from each species to produce fertile offspring. For example, humans are one species and dogs are another species. Individuals of the same species can reproduce to make more individuals of the same species.

answer; (c); /out to the side and directly under the dogs neck.