A Friend of Yours Knocks on His Head with One

Multiple Choice

A friend of yours knocks on his head with one hand while knocking on a wooden table (out of sight) with the other. The knocking sound is perfectly timed with the movements of his visible hand. This leads to the irresistible perception that his head is made of wood and illustrates the Gestalt principle of

A) contiguity.
B) nearness.
C) continuation.
D) common region.