What is the function of a nematocyst?
a. locomotion
b. prey capture
c. digestion
d. sensory perception

The main function of the nematocyst is prey capture. The correct option among all the options given in the question is option "B". The nematocysts are used by Cnidarians like hydra, jellyfish etc. It is actually a specialized capsule that contains venom and it is used to paralyze and capture small preys for food and also to sting any enemy that comes near.

The answer is letter B.

Jellyfishes are known to have this type of structure in their bodies. They capture prey without the aid of teeth, jaws, and hard protective body parts. The nematocysts are stingers that primarily function for capturing prey and secondarily as a defense mechanism. These structures contain toxins that immobilize prey, while others entangle and hold onto their meals by wrapping them around their nematocyst.