Find the Largest Open Intervals Where the Function Is Concave $f(x)=\frac{x}{x^{2}+1}$

Multiple Choice

Find the largest open intervals where the function is concave upward.
- $f(x) =\frac{x}{x^{2}+1}$ (exact values)

A) $(-\infty,-1) ,(-1, \infty)$
B) $(\sqrt{3}, \infty)$
C) $(-\infty,-1)$
D) None