Which of these best shows that snails are not closely related to crayfish?
a. Snails are terrestrial, and crayfish are aquatic.
b. Snails have a broad foot, and crayfish have jointed appendages.
c. Snails are hermaphroditic, and crayfish have separate sexes.
d. Snails are insects, but crayfish are fishes.
e. Snails are bivalves, and crayfish are chelicerates.