Which of the Following Events Most Intrigued Pavlov and Led

Multiple Choice

Which of the following events most intrigued Pavlov and led to his discoveries?

A) The dogs seemed to enjoy the food.
B) The assistant salivated along with the dogs when the dogs started to eat.
C) The dogs stopped salivating after seeing the assistant so many times.
D) The dogs started to salivate when they saw Pavlov's assistant and at the time of day they were usually fed.