Francis enjoys spending time with his girlfriend, Carla. Carla will often eat a large number of grilled onions before spending time with Francis. One day, Francis walks by a hot dog stand and smells some fresh grilled onions. Suddenly, Francis has a great desire to see Carla. What is the neutral stimulus (NS) in this scenario?

Aspending time with Carla
Ba hot dog stand
Cgrilled onions
Dspending time with Francis