Which of the Following Tests Would Be an Example of a Distribution-Free

Multiple Choice

Which of the following tests would be an example of a distribution-free procedure?

A) The t test for population mean $\mu$
B) The paired t test for the expected difference $\mu _ { D }$
C) The F test for two or more population means
D) The Wilcoxon rank-sum test
E) Only A and B are correct tests