Question

which organism has a nerve net that allows it to respond to a stimulus in a coordinated way?
clam
earthworm
shark
hydra

Explanation:

Hydra, a cnidarian, has a nerve net. A nerve net is a diffuse network of neurons that allows for coordinated responses to stimuli. Clams (mollusks) have a more centralized nervous system with ganglia. Earthworms (annelids) have a ventral nerve cord with ganglia. Sharks (fish, vertebrates) have a highly developed central nervous system with a brain and spinal cord.

Answer:

hydra