In Constructing a Confidence Interval Estimate for the Difference Between

In constructing a confidence interval estimate for the difference between two population proportions, we: $\begin{array}{|l|l|}\hline A&\text { pool the population proportions when the populations are normally distributed.}\\\hline B&\text {pool the population proportions when the population means are equal. }\\\hline C&\text { pool the population proportions when they are equal}\\\hline D&\text { never pool the population proportions.}\\\hline \end{array}$