have produced about 520 million tons of methane per

　　year—similar to the total amount of methane produced today by natural and man­made sources.

　　However, the researchers warn that their numbers are estimates based on

　　multiple assumptions about the digestive systems and populations of dinosaurs.

　　The author of the study David Wilkinson says the

　　emission of methane from dinosaurs would have been just

　　one of the causes of warm climate during the Mesozoic era.

　　Other

　　causes

　　include

　　gases

　　produced

　　from

　　volcanoes,

　　swamps, shallow seas and so on. Still, Wilkinson says，“

　　The amount of methane from dinosaurs is large enough to

　　have a measurable effect.”

　　文章大意：一项研究发现，中生代全球变暖很可能是因为恐龙释放出了大量的甲烷。

　　1．Scientists think dinosaurs may have led to the global

　　warming because ________.

　　A．they ate everything they found

　　B．they usually had a good appetite

　　C．they released a lot of methane

　　D. there were too many dinosaurs on earth

　　答案：C　细节理解题。根据第一段的最后一句可知，恐龙导致全球变暖是因为它们释放出了大量的甲烷。

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