Determine Which of the Following Is Not True for the Graph

Multiple Choice

Determine which of the following is not true for the graph of $f ( x ) = \frac { 4 } { x ^ { 2 } + 1 }$

A) ƒ has no relative maximum.
B) ƒ has no relative minimum.
C) ƒ has no vertical asymptote.
D) ƒ has a horizontal asymptote: y = 0.
E) ƒ is concave downward on $\left( - \frac { \sqrt { 3 } } { 3 } , \frac { \sqrt { 3 } } { 3 } \right) \text {. }$