Answer:
The correct answer is giant clam.
Step-by-step explanation:
Clams are not arthropods, they're actually mollusks, specifically bivalves. All of the other options classify as arthropods, even the crabs, that also are arthropods. Also, the spiders are arthropods, although they're not hexapods. Therefore, clams are the only individuals that don't belong to the arthropods.