Suppose You Have Obtained a Confidence Interval for μ,But Wish

Multiple Choice

Suppose you have obtained a confidence interval for μ,but wish to obtain a greater degree of precision.Which of the following would result in a narrower confidence interval?
I.Increasing the sample size while keeping the confidence level fixed
II.Decreasing the sample size while keeping the confidence level fixed
III.Increasing the confidence level while keeping the sample size fixed
IV.Decreasing the confidence level while keeping the sample size fixed

A) I,III
B) III,IV
C) II,III
D) II,IV
E) I,IV