Samantha's cat salivates in response to the taste of food in its mouth. Each morning, Samantha places the food on the back porch. When the door to the porch opens, a bell rings. So, each time she opens the door the bell rings. Now, Samantha's cat salivates when the bell rings. Which of the following is the unconditioned response in this example?

A) food
B) salivation
C) the door
D) the bell on the door Lhe bell on the door