The correct answer is b) population.
A population is defined as a group of individuals of the same species that live in the same area and have the potential to interbreed. Unlike a clan, which may refer to social or familial groups, or a cohort, which often refers to a group of individuals sharing a common demographic characteristic (like year of birth), a population specifically focuses on the biological aspect of a species. Understanding populations is crucial in ecology and conservation, as they are essential for studying species dynamics and health.