Must a Genus Have Both Species and Real Referents That

Multiple Choice

Must a genus have both species and real referents that exist in the world?

A) It must have species, but not real referents.
B) It must have real referents, but not species.
C) It must have both species and real referents.
D) It does not need to have either species or real referents, but it might have them anyway.
E) It does not need to have either species or real referents, and it cannot have them at all.