In Social Learning, What Is Meant by 'Stimulus Enhancement

In social learning, what is meant by 'stimulus enhancement'?

A) The fact that some objects have an obvious use that doesn't need to be learned (e.g. hollowed objects can act as containers)
B) Rewarding an animal for interacting with an object.
C) Having another individual draw attention to an object increases the likelihood that the observer will engage with the object.
D) Certain stimuli are primary reinforcers during social learning.