Kareem Laughs Whenever His Neck Is Touched

Multiple Choice

Kareem laughs whenever his neck is touched. Now before touching his neck, his mommy says "gotcha." Pretty soon, as soon as she says "gotcha," Kareem starts to laugh. In this example, what is the neutral stimulus?

A) Laughing when his neck is touched
B) Saying "gotcha"
C) Laughing when he hears "gotcha"
D) Touching his neck