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

Multiple Choice

Find the largest open interval where the function is changing as requested.
-Increasing $f(x) =\frac{1}{x^{2}+1}$

A) $(1, \infty)$
B) $(-\infty, 0)$
C) $(0, \infty)$
D) $(-\infty, 1)$