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.

the federal government of the united states was established by the constitution. us is a presidential republic. the president is head of state, head of government and of a two party legislative and electoral system. the supreme court balances the powers of the federal and the state government. yhe executive branch is headed by the oresident. there are two chambers of congress, the senate and the house of representatives. judicial power is exercised by the judicial branch (or judiciary), comprised of the supreme court and lower federal courts. the judiciary's function is to interpret the   constitution as well as the federal laws and regulations.