Fossils of the arm of a sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of the Greater Antilles Islands
(A)sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of
(B)sloth, that they found in Puerto Rico in 1991, has been dated at 34 million years old, thus making it the earliest mammal known on
(C)sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of
(D)sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the 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
题目分析：A中的it按照A的表达方式应该和前面的逻辑主语（fossils）保持一致，但是根据意思我们知道it应该指sloth，干掉。B中的they没有指代的东西，干掉。C中的this犯了了A类似的错误，干掉。D后面用sloth，避免了A犯的错误，留着。E中was dated和made有两个谓语了，干掉。
