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Fossils of the arm of a sloth found in Puerto Rico 1991, and dated at 34 million years old , made it the earliest known mammal of the Greater Antilles island. 

B. sloth , that they found in Puerto Rico in1991, has been date at 34 billion years old , thus making it the earliest mammal known on

C. sloth that was found in Puerto Rico in 1991, was dated at 34 billion years old, making   this the earliest known of

D. sloth , found in Puerto Rico in 1991 , have been dated at 34 million years old , making the sloth teh earliest known mammal on

E.  sloth which , found in Puerto Rico in 1991 , was dated at 34 million years old , made the sloth the earliest known mammal of   

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看不懂

用排除法的话，只能选A

有答案吗？

这道题考逻辑关系，不是FOSSILS是sloth成为最早的不如动物，而是was dated at 34 billion years old使sloth成为最早的哺乳动物。

a 逻辑不对

b d 时态错误

e结构混乱，was dated at 34 million years old , made the sloth the earliest known mammal of  两个结构可以看起来都是修饰WHICH，这样句子少主语，即使只有WAS DATED这个部分修饰which，也犯了A中的逻辑错误

高手!讲解的很清楚

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