Answer:
Option B, Conditioned stimulus
Step-by-step explanation:
Conditioned stimulus is a stimulus that gets associated with a non neutral act .
Here, if salvation had taken place after smelling the food then it would have been an Unconditioned stimulus. But here "walking towards the front step" is an act that got associated with the salvation act which is a conditioned response .
Here a famous case of dog , food and bell can be seen for a better understanding.
a) Unconditioned stimulus - Smell of delicious food
Unconditioned response - salvation of dog
b) Now if a dog while feeding is made to hear some bell sound, then in near by future if he ever listens that bell sounds (Conditioned stimulus) he will associate it with food and ultimately will start salivating (Conditioned response)