Which one of these groups has the most organisms?

A. class

B. genus

C. order

D. phylum

Answer: option D) phylum

Explanation:

The linnaean system of classification from largest to smallest level is as follows:

Kingdom - --> phylum - --> class - --> order - --> family - --> genus - --> specie.

Since the phylum level consists of organisms with less similar characteristics compared to class, order and genus, we can safely say it has most organisms.

Thus, phylum is the answer.