Alec Wants to Train His Dog Magnus to Sit on Command

Multiple Choice

Alec wants to train his dog Magnus to sit on command. To achieve this goal, Alec starts by giving Magnus a strip of bacon and saying "sit" every time Magnus sits. A day later, Alec gives Magnus a strip of bacon and a pat on the head and says "sit" every time Magnus sits. Magnus seems to learn to sit on command. However, after a few days of training, Alec notices that Magnus now salivates and wags his tail whenever he hears the word "sit."
-Which of the following stimuli is most likely going to make Magnus salivate

A) Seeing another dog sit down.
B) Hearing the word "set".
C) Being told to lay down.
D) Alec demonstrating sitting down.