In an Experiment Studying Classical Conditioning,a Tone Sounds and 0

Multiple Choice

In an experiment studying classical conditioning,a tone sounds and 0.5 seconds later a puff of air is delivered to a participant's eye.The participant blinks.This process is repeated once per minute.After a number of trials,the participant blinks as soon as the tone sounds and before the puff of air is actually delivered.Within the context of this example,what is the US?

A) the puff of air
B) the tone
C) the time interval
D) the blinking