Which of the Following Statements Is Most Nearly Correct,other Things

Multiple Choice

Which of the following statements is most nearly correct,other things being equal?

A) Using Student's t instead of z makes a confidence interval narrower.
B) The table values of z and t are about the same when the mean is large.
C) For a given confidence level,the z value is always smaller then the t value.
D) Student's t is rarely used because it is more conservative to use z.