Answer:
Option D, a group of organisms that can mate with each other and produce fertile offspring
Explanation:
Organisms belonging to a certain species are sexually compatible in mating or interbreeding. They have the natural potential to mate and produce offspring that can further mate with each other to produce further fertile offspring and this process must go on. An organism that reproduce asexually cannot be easily classified into a species. Also hybrid organism (that reproduce both sexually and asexually) cannot be classified into species.
Hence, option D is correct
