Why Do Some Geologists Believe a Meteorite Impact Was Not

Why do some geologists believe a meteorite impact was not the sole cause of the extinction event at the end of the Mesozoic?

A) Iridium is not always found at the boundary between Cretaceous and Paleogene rocks.
B) Meteorite impacts cause local extinctions, not global extinctions.
C) The meteorite hit at the end of the Jurassic, while extinctions occurred throughout the Cretaceous.
D) The location of an impact crater has not been discovered, and likely never will be.
E) Terrestrial and marine extinctions have not been shown to occur at the same time.