Which of the Following Correctly Describes Degrees of Freedom

Multiple Choice

Which of the following correctly describes degrees of freedom?

A) They are equal to the difference between the point estimate located at the interval center and either the lower or upper limit of the interval between which the parameter is "free to move."
B) They determine the shape of the t-distribution, and refer to the number of independent squared deviations inthat are available for estimatingand, in this sense, can be "freely chosen."
C) They equal sample size minus 2 in the case of a single sample.
D) None of these.
E) All of these.