An acceleration of the head in any plane causes:

    a.    the jelly-like substance in one of the semicircular canals to move to another canal.
    b.    fluid to spill out from the otolith organs into the semicircular canals.
    c.    hair cells to become stiff and straight.
    *d.    the jelly-like substance in one of the semicircular canals to push against hair cells.