William is taking part in an experiment. William is instructed to tickle his own nose, and as a result, he is about to sneeze. Before he sneezes, a research assistant shines a light in his eyes. After many repetitions of this behavior, when the research assistant shines a light in his eyes, William feels like he has to sneeze.





What is the conditioned stimulus (CS) in this scenario?



A.

William tickling his own nose


B.

William sneezing


C.

the light


D.

the researcher’s presence