Which is called as the brain of the nematode?

Answer: Option C

Nerve ring is called the brain of the nematode.
The nerve ring receives sensory input from the anterior tip of the animal using six nerve bundles, all nerve fibers of which have centrally located cell bodies.
The central nervous system consists primarily of a so-called circumoral brain or nerve ring, consisting of annular neuropil that encircles the neck of the pharyngeal muscle.