Which statement correctly describes the behavior of the graph of g(x)=x−2x2−5x+4 at x=2?
a) The graph has a horizontal tangent at x=2 because g′(2)=0.
b) The graph has a vertical tangent at x=2 because g′(2) is undefined while g(2) exists.
c) The graph has no tangent at x=2 because g is not defined there.
d) The graph has a tangent of slope 1 at x=2 after canceling a common factor.