Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the question. You have learned about dinosaurs in school. Maybe you have seen them in museum. But how much do you really know about these animals? Not all dinosaurs were just big reptiles. For years, scientists thought dinosaurs were big, dumb, and cold blooded - in other words, just giant reptiles. Some dinosaurs were huge. But many were about the size of modern-day birds or dogs. Were ...

Read the following passage and mark the letter A, B, C, or D to indicate the correct answer to each of the question.

You have learned about dinosaurs in school. Maybe you have seen them in museum. But how much do you really know about these animals? Not all dinosaurs were just big reptiles. For years, scientists thought dinosaurs were big, dumb, and cold blooded - in other words, just giant reptiles. Some dinosaurs were huge. But many were about the size of modern-day birds or dogs. Were dinosaurs warm- or cold blooded? Paleontologists- are not sure. But they believe some were intelligent. Of course, no dinosaur was as smart as a human or even a monkey. However, some smaller dinosaurs - like the two-meter (six-foot) Troodon — had fairly large brains.

Was Tyrannosaurus rex a powerful predator? Some scientists think the opposite is true. In the movies, T.rex is often a speedy giant, but in fact, this dinosaur could not run very fast. Physically, it was too large. In reality, T.rex probably moved as fast as an elephant. Also, T. rex had very small arms. Without strong legs or arms, this dinosaur probably wasn’t a powerful hunter. It may have been a scavenger instead, only eating animals that were already dead.

Did an asteroid kill the dinosaurs? An asteroid hit Mexico’s Yucantan Peninsula about 65 million years ago. It created a 180-kilometer (HO-mile) wide crater called Chicxulub. Many believe this asteroid caused the extinction of the dinosaurs. But even before this, dinosaurs were already dying out around the world, for many reasons. At the end of the Cretaceous period, for example, the global climate was changing and Earth's temperature was getting colder.Dinosaurs completely disappeared about 65 million years ago. However, scientists believe modern-day birds are descendants of certain dinosaurs. If this true, then dinosaurs' relatives are still walking - and flying - among us!

(Source: https://www.ducksters.com/animaIs/dinosaurs)

The word “it” in paragraph 2 refers to _______?