Three-month-old Lionel loved to suck on his fingers. He was quite fond of putting his fingers into his mouth and then pulling them out only to look them over for a minute or two before putting them back into his mouth
He repeated this behavior over and over. Lionel's behavior with his fingers illustrates a:________.
a. simple reflex.
b. secondary circular reaction.
c. primary circular reaction.
d. tertiary circular reaction.