An Infant's Sibling Always Jumps Off His Bed with a Loud

Multiple Choice

An infant's sibling always jumps off his bed with a loud bang when he wakes up from his nap. He then comes downstairs and greets the infant with a tickle, making the infant laugh and cough reflexively. Eventually, the infant begins to laugh and cough reflexively when he hears the bang, even before he sees his brother. In this scenario, the loud bang is a(n) :

A) conditioned stimulus.
B) unconditioned stimulus.
C) conditioned response.
D) unconditioned response.