For each statement below, determine which graph(s) show that the statement is incorrect.
(GRAPH NOT COPY)
(a) Every rational function has a vertical asymptote.
(b) Every rational function has at least one vertical, horizontal, or slant asymptote.
(c) A rational function can have at most one vertical asymptote.
(d) The graph of a rational function with a slant asymptote cannot cross the slant asymptote.