Based on the fact that Shara becomes nauseous from smelling cooked shellfish, the conditioned stimulus is the smell of cooked shellfish.
This refers to a stimulus that affects a person in certain way even though this was not always the case.
The person reacts to that stimulus because something happened to them that transformed that stimulus into something that could affect them. This is what happened to Shara when the smell of cooked shellfish became a trigger for nausea.
Find out more on conditioned stimulus at https://brainly.com/question/26056083.