Find all rational zeros of the polynomial function below.
f(x) = 3x^3 - 13x^2 - 59x + 21
Select the correct choice below and, if necessary, fill in the answer box to complete your choice.
A. The rational zero(s) of the function is/are
(Simplify your answer. Use a comma to separate answers as needed.)
B. The function has no rational zeros.