Let $$a \in R$$ and let $$f: R \rightarrow R$$ be given by
$$f(x) = x^5 - 5x + a$$
Then

A

f(x) has three real roots if a > 4

B

f(x) has only one real root if a > 4

C

f(x) has three real roots if a < -4

D

f(x) has three real roots if - 4 < a < 4