Which scenario would result in reflex contraction of the extensor muscles of the right leg?       a.      Increasing the frequency of action potentials from muscle spindles in flexor muscles of the right leg.       b.      Dropping a hammer on the right big toe.       c.      Increasing frequency of action potentials from Golgi tendon organs in the extensor muscles of the right leg.       d.      Stepping on a tack with the left foot.       e.      Stretching the flexor muscles in the right leg.