| Dinosaurs were reptiles which became
extinct about 65 million years ago. The most intriguing question about dinosaurs
has always been "{{U}} (21) {{/U}}did they die out?" There is no simple
answer to this question,{{U}} (22) {{/U}}many hundreds of scientists are
studying the problem. They are not studying the extinction of the dinosaurs{{U}}
(23) {{/U}}, but the whole question of extinction. Many other plants
and animals have{{U}} (24) {{/U}}in the past, and it is important to
understand{{U}} (25) {{/U}}this happened. Having this information could
help save many species that are{{U}} (26) {{/U}}in the modern world.
Humans are causing extinctions now, because of pollution and other damage{{U}}
(27) {{/U}}the environment. Maybe the dinosaurs can tell us how to
save the earth today,{{U}} (28) {{/U}}their extinction 65 million years
ago! Some of the early dinosaur scientists, 100 years ago, thought the dinosaurs
died out because the{{U}} (29) {{/U}}changed, and they could not
breathe. Others thought that the dinosaurs disappeared simply because they
became too big. They were{{U}} (30) {{/U}}to move and could not find enough food{{U}} (31) {{/U}}One theory is that a huge killer meteorite{{U}} (32) {{/U}}the earth. Some scientists{{U}} (33) {{/U}}that the extinction of dinosaurs was possibly due to rapid{{U}} (34) {{/U}}of the planet's climate. Perhaps huge amounts of lava pours out of volcanoes in India. This sent up vast{{U}} (35) {{/U}}of dust that blacked out the sun, and made the earth icy cold. |