In a formal letter, the date should be shown directly above
a. the return address.
b. the salutation.
c. the inside address.
d. the closing.

The correct answer for the question that is being presented is this one: "c. the inside address." In a formal letter, the date should be shown directly above the inside address. The date should be directly visible to the reader so that it's easier to refer what date it is written and given.