Holding the sample size n constant, which of the following statements is correct?

a.Whenis known, the margin of error,, is fixed and is the same for all samples of sizen.

b.Whenisunknown, the margin of error,, varies from sample to sample because the sample standard deviation s varies depending upon the sample selected.

c.Whenisunknown, the margin of error,, is larger for large values of s and is smaller for small values of s.

d.All of the above