Which one of these statements in relation to the function f(x)=x+ \frac{3}{x} is false? Select one:

a.
f is decreasing on the interval (- \infty , 0)

b.
f is decreasing on the interval (3, - \infty )

c.
The graph of f has a vertical asymptote at x=0

d.
The graph of f is concave down on (- \infty , 0)

e.
The graph of f is concave up on (0, (- \infty )