A Study Based on OLS Regressions Is Internally Valid If

Multiple Choice

A study based on OLS regressions is internally valid if

A) the errors are homoskedastic, and there are no more than two binary variables present among the regressors.
B) you use a two-sided alternative hypothesis, and standard errors are calculated using the heteroskedasticity-robust formula.
C) weighted least squares produces similar results, and the t-statistic is normally distributed in large samples.
D) the OLS estimator is unbiased and consistent, and the standard errors are computed in a way that makes confidence intervals have the desired confidence level.