Which of the following is not an arthropod?

Question

Earthworm, crayfish, grasshopper, or a tick

Answer 1

If we know what kinds of characteristics an arthropod has, we can identify what kinds of organisms fit these descriptions. We know that arthropods have exoskeletons made of chitin, they have segmented bodies, they are bilaterally symmetrical, they have a ventral nervous system, they have jointed limbs, and highly developed sense of organs. Looking at the list given above, it seems that grasshoppers, ticks, and crayfish all are arthropods.