For a Sample of Size 25 Observations Taken from a Normally

For a sample of size 25 observations taken from a normally distributed population. The sample standard deviation is 6, a 95% confidence interval estimate for the population mean would require the use of: $\begin{array}{|l|l|}\hline A&\text { z=1.96 }\\\hline B&\text { t=1.711 }\\\hline C&\text {z=1.645 }\\\hline D&\text {t=2.064 }\\\hline\end{array}$