Otolith is formed of-
a. Carbohydrates
b. Magnesium
c. Lipid
d. Calcium Carbonate

Hint: The otolith organs sense gravity and lined acceleration often as from due to the beginning of the movement in a straight line. Persons or animals deprived of otolith organs or faulty otoliths have minor abilities to sense motion as well as direction to gravity. Analogous balance receptors called statocysts can be visible in numerous invertebrate groups but are not contained in the assembly of an inner ear.

Complete answer:
The otolith organs detect motion conferring to their orientation. The utricle is horizontal in the head, and mainly registers accelerations performing in the horizontal plane of the head.
Studies reveal that otoliths are not formed of carbohydrates, magnesium, or lipids as they don’t play any role in gravity and steadiness.

Otolith is also called statolith or otoconium. The otoconia are composed of calcium carbonate. Fused with a protein matrix protein (around 40% of the volume). These are the crystals created up of calcium carbonate and located in the utricle or saccule of the inner ear. These are used as route, gravity, steadiness, and movement indicators in vertebrates and advanced terrestrial and aquatic vertebrates; they execute the function of sound detection too. Otoliths are delicate to linear acceleration and gravity.

Hence, the correct answer is option (D).

Note: Otoliths are involved as movement and guiding indicators among all vertebrates and have a secondary purpose in sound detection in developed aquatic and terrestrial vertebrates. They are sensitive to gravity and linear acceleration. Due to their head orientation, the utricle is sensitive to a change in horizontal movement, and the saccule gives information about vertical acceleration. As mentioned, Mollusks statocysts are of similar morphology to the displacement-sensitive organs of vertebrates.