Find the Largest Open Intervals Where the Function Is Concave $f(x)=\frac{6}{x}$

Multiple Choice

Find the largest open intervals where the function is concave upward.
- $f(x) =\frac{6}{x}$

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