Answer:
D. a rightward shift in the demand curve for hamburgers.
Explanation:
A rightward shift in demand curve refers to an increase in demand for a product. The implication is that a larger quantity is demanded at each market price.
In the scenario, at the steve demanded more hamburgers at the given price without increase in income or increase in the price of a related good; hence there is no income or substitution effect
The demand of a product can shift due to certain reasons one of which is consumer expectations
Steve expected the price to be $2 but it was $1 hence he had to demand for more hamburgers.