Dinosaurs died out long before people appeared. Dinosaurs lived from about 230 million years ago to
about 65 million years ago. There are several theories about why dinosaurs became extinct.
Many scientists believe that there was a sudden, (22) _____ event. They think that an asteroid or
comet (23) _____ with the earth. Fire from the impact burned large areas. Dust blocked sunlight from (24)
_____ the surface of the earth. Acid rain fell everywhere. Plants could not grow. There was no food for the
plant-eating dinosaurs, so they died out.
Other scientists think that the environment changed. Maybe the (25) _____ grew colder and dinosaurs
slowly became extinct over several million years. Many scientists think that birds descended from a small
kind of dinosaur. If this is true, then dinosaurs are still (26) _____ in the form of modern birds.
22. A. violet B. violence C. violent D. violently
23. A. crashed B. collided C. confronted D. met
24. A. reaching B. arriving C. approaching D. coming
25. A. days B. atmosphere C. weather D. climate
26. A. lively B. alive C. living D. live
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Sinh Học lớp 12
