If $f(x)$ is a continuous function such that $f^{\text{'}\text{'}}(x)=5x^2-4,$ and $x=0,x=3,$ and $x=-3$ are critical values, then by using the second derivative lest, we can concuide that

A$.x=-3,0,3$ are points of inflection

B$.$ Nothing can be concluded

C$.x=-3,3$ are relative minimums and $x=0$ is a relative maximum

D$.x=-3,3$ are relative maximums and $x=0$ is a relative minimum