The correct option is B Equilibrium
The statocysts are the equilibrium organs of snails. They are capsules or vesicles filled with liquid, calcareous grains or statoliths floating within. As soon as the snail moves or changes its position, inertia has the statoliths float against the statocyst's wall. There, sense hair or cilia detect the contact which is then processed to the nervous system.
So, the correct answer is option C.