Which of the following statements is not true about a rational function of the form f(x)= g(x)/h(x) where g and h are polynomial functions?
a) Vertical asymptotes occur where h(x) = 0 and g(x) is non-zero.
b) The domain of the rational function is all real numbers except where h(x) = 0.
c) Holes in the graph can occur when g(x) and h(x) have common factors that cancel out.
d) Horizontal asymptotes can only be horizontal lines.