What does it mean to say that the confidence interval methods for the mean are robust against departures from​ normality? choose the correct answer below.
a. the confidence interval methods for the mean are robust against departures from​ normality, meaning they only work with distributions that​ aren't normal.
b. the confidence interval methods for the mean are robust against departures from​ normality, meaning they work well with distributions that​ aren't normal, provided that departures from normality are extreme.
c. the confidence interval methods for the mean are robust against departures from​ normality, meaning they work well with distributions that​ aren't normal, provided that departures from normality are not too extreme.
d. the confidence interval methods for the mean are robust against departures from​ normality, meaning they​ don't work well with distributions that​ aren't normal?