The correct answer is d, price of the product.

Determinants of demand are factors that can cause a shift in the entire demand curve. These determinants include factors such as income of consumers, number of buyers, price of related goods, tastes and preferences, consumer expectations, and other factors that can influence the quantity demanded at each price level.

The price of the product itself, however, is not a determinant of demand. Instead, it is a determinant of quantity demanded, as it represents a movement along the demand curve. A change in price will result in a movement along the demand curve, while changes in other determinants will cause a shift in the entire demand curve.