Consider the Following Model: Q^d = F(P,P^s,P^c,INC)

Consider the following model: Q^d = f(P,P^s,P^c,INC)
Where Q^d is quantity demanded of a particular product per month,P is the price of the product,P^s is the price of substitutes,P^c is the price of complements,and INC is monthly income.
This equation represents

A) a non-linear model
B) an economic model
C) an econometric model
D) a challenge to the law of demand.