The correct option is A Ommatophores
Pila or other mollusc has a pair of small, black eyes, each situated on a short stalk called the ommatophore, which arises outside the true tentacle of its side.
Osphradium is a single structure that hangs from the roof of the pulmonary chamber close to its entrance and is oval in shape.
The operculum is the thin, flat-lid like structure by which the mouth is closed.
Ostracum is the thickest layer of the shell of a mollusc and is composed of alternating layers of calcium carbonate and conchiolin running at right angle to the margin of the mouth of a shell.
So, the correct answer is option D.