Which of These Definitions of Species BEST Matches the Biological

Multiple Choice

Which of these definitions of species BEST matches the biological species concept?

A) Members of the same species are all morphologically similar.
B) Members of the same species are all genetically identical.
C) Members of the same species look almost exactly alike.
D) Members of the same species are whatever an expert says they are.
E) Members of the same species can mate and produce fertile offspring.