Tracy Suffered from Nausea for the First Three Months of Her

Tracy suffered from nausea for the first three months of her pregnancy. Because it was easy, her husband ordered Chinese take-out food three or four evenings each week. In spite of her nausea, Tracy forced herself to eat the take-out food. A year later, she and a friend walk past a Chinese restaurant and the smell of the food makes her nauseated. Which of the following explains why Tracy developed an aversion to the food but her husband did not?

A) biological preparedness
B) instinctive drift
C) spontaneous recovery
D) observational learning