Consider the following regression model: y = 0 + 1 x 1 + u. Which of the following is a property of Ordinary Least Square (OLS) estimates of this model and their associated statistics?
a.The point (X,Y) always lies on the OLS regression line.
b.The sum of the OLS residuals is negative.
c.The sum, and therefore the sample average of the OLS residuals, is positive.
d.The sample covariance between the regressors and the OLS residuals is positive.