when we have power function or exponential, or then we have a/x, then functions are not going to give arithmetic sequence, because an arithmetic sequence it is really a linear function when x are natural numbers,
so we need to check only A
f(x)=- x/3 +5
x 1 2 3 4 5
y 14/3 13/3 12/3 11/3 10/3 arithmetic difference is -1/3
so the answer is A
