What Does an Invertebrate Statocyst Contain, Which Surrounds Movable Elements

What does an invertebrate statocyst contain, which surrounds movable elements, so that changes in body position move the latter and thus trigger an action potential?

A) efferent neurons, which surround statoliths
B) statoliths, which surround sensory hair cells
C) otoliths, which surround sensory hair cells
D) sensory hair cells, which surround statoliths