Question

which category? able to swim most its life hydrozoa scyphozoa anthozoa

Explanation:

Scyphozoa (jellyfish) are known to be able to swim for most of their life cycle. Hydrozoa may have sessile stages, and Anthozoa (like corals, sea anemones) are mostly sessile or attached, not swimming most of their life.

Answer:

B. Scyphozoa