The author implies that if the theory described in the third paragraph is true, which one of the following would have been true of iridium in the atmosphere at the end of the Cretaceous period? A. Its level of concentration in the Earth's atmosphere would have been high due to a slow but steady increase in the atmospheric iridium that began in the early Cretaceous period. B. Its concentration in the Earth's atmosphere would have increased due to the dramatic decrease in sea level that occurred during the Cretaceous period. C. It would have been directly responsible for the extinction of many ocean species. D. It would have been more uniformly dispersed than iridium whose source had been the impact of a meteorite on the Earth's surface. E. It would have been more uniformly dispersed than indium released into the atmosphere as a result of normal geological processes that occur on Earth.