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

Multiple Choice

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

A) $(-\infty,-1)$
B) None
C) $(-1, \infty)$
D) $(-\infty, \infty)$