A. Joshua took a nap after sorting the mail.

Joshua sorted the mail, then took a nap? Seems pretty logical to me and it shows a relationship. (sort –>nap)

B. Joshua took a nap while sorting the mail.

Joshua napping and sorting mail at the same time? Possible, but probably not logical.

C. Joshua took a nap before sorting the mail.

Joshua took a nap then sorted the mail? Also logical, also shows a relationship. (nap–>sort)

D. Joshua took a nap instead of sorting the mail.

Joshua naps and doesn’t sort the mail? Also logical, shows a relationship (nap=not sort)

So A, C, and D work.

If you have to pick one, I would guess A because there is a relationship based on the assumption of average human behavior (sorting would make Joshua tired, so he would take a nap afterward), but if this is a test question with only one correct answer, this is just one of those tests that are totally unfair and need to be destroyed or saved as an example of how not to design a test. (Rule 1: Don’t write multiple choice questions with multiple correct answers!)

Yep, Joshua took a nap after sorting the mail.