Which of the following, if true, most strongly supports the scientist's conclusion? A. Volcanoes massive enough to generate high concentrations of iridium are very rare. B. Massive volcanic eruptions occurred frequently 80 million years ago. C. Most scientists support the hypothesis that a cosmic impact wiped out the dinosaurs. D. The massive extinction that occurred 70 million years ago killed not only the dinosaurs but also 70 percent of all life on Earth. E. A comet struck the earth some 120 million years ago, but no widespread extinction occurred.