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　　托福阅读修辞目的题：The Cambrian Explosion

　　【Paragraph 6】A third fossil formation containing both soft-bodied and hard-bodied animals provides evidence of　the result of the Cambrian explosion. This fossil formation, called the Burgess Shale, is in Yoho National Park in the　　Canadian Rocky Mountains of British Columbia. Shortly after the Cambrian explosion, mud slides rapidly buried　thousands of marine animals under conditions that favored fossilization. These fossil beds provide evidence of about 32　modern animal groups, plus about 20 other animal body forms that are so different from any modern animals that they　　cannot be assigned to any one of the modern groups. These unassignable animals include a large swimming predator　called Anomalocaris and a soft-bodied animal called Wiwaxia, which ate detritus or algae. The Burgess Shale formation　also has fossils of many extinct representatives of modern animal groups. For example, a well-known Burgess Shale　animal called Sidneyia is a representative of a previously unknown group of arthropods (a category of animals that　includes insects, spiders, mites, and crabs).(The Cambrian Explosion)

　　Why does the author mention “Anomalocans” and “Wiwaxia”?

　　○ To contrast predators with animals that eat plants such as algae

　　○ To question the effects of rapid mud slides on fossilization

　　○ To suggest that much is still unknown about animals found in the Burgess Shale

　　○ To provide examples of fossils that cannot be assigned to a modern animal group

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