In which group are jellyfish classified?

Jellyfish are classified within the phylum Cnidaria, which includes several different classes that encompass various types of jellyfish. The correct answer indicates that jellyfish belong to multiple classifications based on their characteristics and life stages.

Hydrozoa is a class that includes some jellyfish, though it's more commonly recognized for its polyp and medusa forms, which can resemble jellyfish. Scyphozoa is the class that primarily comprises the large common jellyfish that many people visualize when they think of jellyfish. Cubozoa includes box jellyfish, which are known for their cube-shaped medusa and potent venom.

Since jellyfish can be found in all these classes, saying "all of the above" is accurate because it reflects the diversity within the jellyfish taxonomy, thereby encompassing various types classified under different classes within the Cnidarian phylum.