In which of the following scenarios will conducting a paired $t$-test for means be appropriate? CHECK ALL THAT APPLY.


A. To test if the proportion of low-income families is higher than that of high-income families in British Columbia.

B. To test if there is a difference between the mean number of CD4 T cells in healthy patients and patients with cancer.

C. To test if there is a difference between the mean annual income of male British Columbians and that of female British Columbians.

D. To test if there is a difference between the mean number of antibodies in patients before surgery and after surgery.

E. To test if there is a difference between the mean annual income of husbands and that of their wives in Canada.

F. To test if the mean annual income of Ontarians is higher than that of British Columbians.

G. None of the above