Which sum is rational

A.
B.
C.
D.

Asequence is defined recursively using the formula f(n + 1) =f(n) - 5. which sequence could be

Aubrey read 29 books and eli read 52 books what number is equal to the number of books aubrey read?

Aword processing program requires a 7- digit registration code made up of the digits 1,2,4,5,6,7 and 9 each number has to be used and no number can be used mor than once how many codes are possible