Answer:
D. Genetic
Step-by-step explanation:
Golden retriever is a breed of species of dogs "Lupus". It is classified under subspecies "familiaris". Since the scientists are studying diversity of disease prevalence in golden retrievers, their objective is to study the genetic diversity of species "lupus". Genetic diversity is defined as genetic variety present within a species. It takes into account of variations present in a given population of the species as well as that of separate populations present in various habitats.