A Multiple Regression Analysis Based on a Data Set That

A multiple regression analysis based on a data set that consists of 500 observations yielded the following estimated demand equation:
Q = 120 - 1.1P + 0.04I + 0.90A - 0.04P_Z
Where P is price, I is income, A is advertising, and P_Z is the price of a related good. If the standard errors of the independent variables are 0.25, 0.5, 0.3, and 0.01, respectively, which of the four variables should be dropped from the equation?

A) P
B) I
C) A
D) P_Z