Find the Interval on Which the Graph Of $f ( x ) = \ln \left( x ^ { 2 } + 1 \right)$

Multiple Choice

Find the interval on which the graph of $f ( x ) = \ln \left( x ^ { 2 } + 1 \right)$ is concave upward.

A) (-1, 1)
B) (-1, 2)
C) (-2, 1)
D) (-2, 2)
E) (-1, 3)
F) (-3, 2)
G) (-3, 3)
H) $( - \infty , \infty )$