The Interesting Thing About Confidence Intervals Established Employing Stratified Sampling

The interesting thing about confidence intervals established employing stratified sampling is that

A) The within-strata variability does not enter into the calculation of the standard error of estimate.
B) The between-strata variability does not enter into the calculation of the standard error of estimate.
C) Neither the within-strata variability nor the between-strata variability enters into the calculation of the standard error of estimate.
D) The confidence interval is wider than that established employing simple random sampling.
E) The sample mean provides a biased estimate of the population mean.