The last caribbean monk seal that died was the last member of
a species.
a community.
a biome.
an ecosystem.

The last Caribbean monk seal that died was the last member of a SPECIE.
All the living things, both plants and animals are placed in a hierarchical order depend on their characteristics and specie is the least stage on that rank. A specie refers to a specific group of animals which share similar physical characteristics. The Caribbean monk seal for instance is one of the specie of fishes that exist on earth.Thus, a specie is a basic unit of classification which recognize animals of the same sort.

A. radioactive dating