After a scary biking accident, Kai extinguished his conditioned fear of bikes by cycling on a safe biking trail every day for a week. The reappearance of his previously extinguished fear when he rode a bike on the same trail two weeks later best illustrates:

Spontaneous recovery.

Explanation: Spontaneous recovery is stern used in Psychology to describe the sudden reappearance of a conditioned response after of it has been extinguished after a certain period of time.

ACCORDING TO PAVLOV A CLASSICAL PSYCHOLIGIST, THE SUDDEN REAPPEARANCE OF AN EXTINGUISHED CONDITIONED RESPONSE OCCURS AFTER A PERIOD OF NOT BEING EXPOSED TO THE CONDITIONED STIMULUS.

answer; curiosity;

answer; make a no-nonsense accusation of the other;