Find the open intervals where the function is concave upward or concave downward. Find any inflection points.

Select the correct choice below and, if necessary, fill in the answer box$($es$)$ to complete your choice.

A$.$ The function is concave upward on the interval$($s$)$ and concave downward on the interval$($s$)$

$($Type your answers in interval notation. Use a comma to separate answers as needed.$)$

B$.$ The function is concave downward on the interval$($s$)$

The function is never concave upward.

$($Type your answer in interval notation. Use a comma to separate answers as needed.$)$

C$.$ The function is concave upward on the interval$($s$)$

$.$ The function is never concave downward.

$($Type your answer in interval notation. Use a comma to separate answers as needed.$)$

D$.$ The function is never concave upward or downward