Most mollusks have shells.
Mollusks are the second-largest invertebrate group.
Most of the second-largest invertebrate group have shells.
what do the second-largest invertebrate group have?

[a] shells
[b] a cuticle
[c] insects
[d] barnacles
[e] animals
[f] tortoises
[g] alveoli
[h] honeybees