Consider the linear model given by Yi = B1 + 82 . Xi + ei, where E (e? ) = of is different for some observations. Then, the LS estimators b1, b2 for 31, 82 are: Select one: a. Unbiased estimates for B1, B2 regardless of the dependence relation between g - and X; O b. BLUE C. Unbiased estimates B1, B2 only if off does not depend on X, d. Biased estimates for B1, B2 only if off i depends on X