Read the passages and answer the questions that follow.
Have you ever wondered why you have never seen a living Tyrannosaurus rex or Velociraptor? These large animals, along with many other species of dinosaur, all became extinct about 65 million years ago. The reason for the mass extinction of over half of Earth’s species is most likely an impact of a huge meteorite. Scientists have discovered a layer of the Earth’s crust that dates to 65 million years ago, which contains large amounts of the element iridium. This element is rare on the Earth’s surface; however, iridium is quite common in meteorites. A crater found in Mexico, also dating back to 65 million years ago, indicates that the iridium probably arrived when an asteroid or comet struck the Earth. The impact would have distributed iridium around the world while also kicking up dust and debris. The debris would have blocked sunlight and hindered plants’ ability to generate energy, causing them to die off. As plants died away, herbivores would lose their food sources and become extinct as well. Ultimately, large carnivores, including T. rex, would follow suit.