Consider the linear regression madel y = B0 + B1x + u, where the regressor x may be correlated with the error term u, We use 2SLS ta estimate the model because the 2SLS estimator af B1 is____ than the OLS estimator of B1. a. easier to implement b. more efficient c. marelikely to be consistent d. ess likely to be affected by heteroskedasticity