Which one of the following, if true, would cast the most doubt on the theory described in the last paragraph of the passage? A. Fragments of meteorites that have struck the Earth are examined and found to have only minuscule amounts of iridium hexafluoride trapped inside of them. B. Most diapir eruptions in the geological history of the Earth have been similar in size to the one that occurred in India at the end of the Cretaceous period and have not been succeeded by periods of climatic change. C. There have been several periods in the geological history of the Earth, before and after the Cretaceous period, during which large numbers of marine species have perished. D. The frequency with which meteorites struck the Earth was higher at the end of the Cretaceous period than at the beginning of the period. E. Marine species tend to be much more vulnerable to extinction when exposed to a dramatic and relatively sudden change in sea level than when they are exposed to a gradual change in sea level similar to the one that preceded the extinction of the dinosaurs.