Seth purchased five pounds of live crayfish and realized that the outer shells were made of a tough carbohydrate similar to that used to make the carapace of a cockroach. What do you think the outer shells of the crawfish are made of?

Calcium Carbonate or Lime Stone

Explanation:

The outer hard shell of cray fish is made up of CaCO3 from sea sediments. It as analogue to the carapace of cockroach because both belongs to the phylum Arthropoda. Although they have different classes but their exoskeleton shares same composition and internal structure. Both use this to protect themselves against predators.