Consider the multiple linear regression model, y = β0 + β1x1 + …+ βkxk + u (1). Which of the following statements is correct?

a. Under Assumptions MLR.1 through MLR.4, E left parenthesis beta with hat on top subscript j right parenthesis equals beta subscript j for any value of βj, j = 1, …, k: beta with hat on top subscript j is an unbiased estimator for βj. b.Unbiasedness is a feature of the sampling distributions of beta with hat on top subscript j ’s, which says nothing about the estimates obtained from a given sample. It is always possible that one random sample, used to estimate (1), gives point estimates far from the true population parameters βj’s. c.Including one or more irrelevant variables in a multiple regression model, or overspecifying the model, does not affect the unbiasedness of the OLS estimators, but it can have undesirable effects of the variances of the OLS estimators. d.All of the above.