Assuming a good random sample was taken which of the following combinations would provide the most precise estimate of U (population mean)?

A. N=40 Sample Mean=8.3 S=3.8

B. N=40 Sample Mean=4.3 S=5.8

C. N=20 Sample Mean=8.3 S=5.8

D. N=20 Sample Mean=4.3 S=3.8

E. N=20 Sample Mean=4.3 S=5.8