Based on a random sample of 50, a 95% confidence interval for the population proportion was computed. Holding everything else constant, which of the following will reduce the length of the confidence interval by half? (CHECK ALL THAT APPLY):

A. Change the confidence level to 68%.
B. Quadruple the sample size.
C. Change the confidence level to 99.7%.
D. Double the sample size.
E. Decrease the sample proportion by half.