In the Equation for Calculating a Confidence Interval for a Proportion

Multiple Choice

In the equation for calculating a confidence interval for a proportion, $p \pm z _ { a / 2 } \sqrt { \frac { p ( 1 - p ) } { n } }$ what does $\sqrt { \frac { p ( 1 - p ) } { n } }$ represent?

A) the mean for the sampling distribution of the proportion
B) the degree of freedom for the sampling distribution of the proportion
C) the standard error for the sampling distribution of the proportion
D) the estimator for sampling distribution of the proportion