Determine Where the Graph of Is Concave Upward and Where

Determine where the graph of is concave upward and where it is concave downward. Also, find all inflection points of the function.

A) concave downward: and
, concave upward:
and
; inflection points:
and

B) concave downward: and
, concave upward:
and
; inflection points:
and

C) concave downward: nowhere, concave upward: and
; inflection points: none
D) concave downward: and
, concave upward: nowhere; inflection points: none