Which is the second-largest phylum in the animal kingdom?

Mollusca:

The second-largest phylum in the animal kingdom is Mollusca.

1. It is characterized by shelled animals with a distinguishable head and foot region.
2. They have comb-like gills called ctenidia.
3. The body is covered by a calcareous shell that may be external or internalized.
4. They exhibit an organ-level body organization.
5. Higher members of the phylum have tentacles, well-defined eyes, and mouthparts.
6. These are aquatic and marine organisms.
7. These are triploblastic.
8. These are bilaterally symmetrical and coelomate.
9. Examples include snails, Chiton, Nautilus, Pinctada, etc.