Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks from 39 to 43
WHY DO ANIMALS GO EXTINCT?
Different kinds of animals have appeared and disappeared throughout Earth’s history. Some animals go extinct because the climate (39) ______ they live changes. The climate may become wetter or drier. It may become warmer or cooler. If the animals cannot change, or adapt, to the new climate, they die. Some animals go extinct because they cannot (40) ______ with other animals for food. Some animals go extinct because they are killed by enemies. New kinds of animals are always evolving. Evolving means that the animals are changing (41) ______ from generation to generation. Small differences between parents, children, and grandchildren slowly add up over many, many generations. Eventually, a different kind of animal evolves. Sometimes many of the animals on Earth go extinct at the (42) ______ time. Scientists call this a mass extinction. Scientists think there (43) ______ at least five mass extinctions in Earth’s history. The last mass extinction happened about 65 million years ago. This mass extinction killed off the dinosaurs.