Homeobox genes, which are critical for the developmental organization of bodies, are found in species as diverse as humans and fruit flies. This shared set of genes indicates that

A) humans and fruit flies are actually closely related to one another.
B) homeobox genes evolved independently multiple times in many different organisms.
C) humans and fruit flies are under similar selective pressures that have led to the evolution of genes with similar functions.
D) these genes originated in a distant common ancestor and have been retained due to their usefulness.