The group that shares the maximum number of common characters is two individuals of a species.
Explanation:
In the taxonomic hierarchy, a species is the most specific group, meaning individuals within a species are very closely related and share the most common characteristics.
Why other options are incorrect:
Two species of a genus:
While species within the same genus are closely related, they still have distinct characteristics that differentiate them from each other.
Two genera of a family:
Genera within a family share even fewer common characteristics than species within a genus.
Two genera of two families:
This represents the least amount of shared characteristics as the genera belong to different families.