Answer: C. That jellyfish have stinging cells, while comb jellies do not
Step-by-step explanation:
Comb Jellies to the untrained eye are the same as Jellyfish but as the question says, they are different in that they belong to different phyla.
The Comb Kelly belongs to the Ctenophora Phylum while the Jellyfish belongs to the Coelenterate phylum.
Perhaps the largest difference between them is that Ctenophora do not have stinging cells as opposed to members of the Coelenterate Phylum that do.