The Demand for Pizzas in a Large Town Is Written

The demand for pizzas in a large town is written as: Q_d = 120 - 10P + 5P_b - 0.5P_s - 10Y,where Q_d is the quantity demanded,P is the price,P_b is the price of burritos,P_s is the price of soft drinks sold in the pizza restaurants,and Y is personal income per month (in thousand dollars) .We can conclude that burritos and pizzas are

A) substitutes.
B) normal goods.
C) complements.
D) unrelated.