In this question, C = consumer spending, Y = income, r = the rate of interest, and P = prices. From the expression C = C(Y,r,P), we know that:
A) C is the product of Y, r, and P
B) any change in C must be caused by a change in P
C) changes in C will cause changes in Y, r, and P
D) Y, r, and P are independent variables