Find the Largest Open Interval Where the Function Is Changing $f(x)=x^{3}-4 x$

Multiple Choice

Find the largest open interval where the function is changing as requested.
-Decreasing $f(x) =x^{3}-4 x$

A) $\left(-\frac{2 \sqrt{3}}{3}, \frac{2 \sqrt{3}}{3}\right)$
B) $\left(\frac{2 \sqrt{3}}{3}, \infty\right)$
C) $(-\infty, \infty)$
D) $\left(-\infty,-\frac{2 \sqrt{3}}{3}\right)$