再请教一个。汗！

Q17:

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.

1. sloth found in Puerto Rico in 1991, and dated at 34 million years old, made it the earliest known mammal of
2. 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
3. sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of
4. sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on
5. sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliest known mammal of

答案是D，但我选择的是E,印象中date不能用于完成时态吧

E的结构很混乱，存在逻辑问题：

Fossils of the arm of a sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliest known mammal of the Greater Antilles islands

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Fossils made the sloth the earliest?

date, 确定。。的日期，可以用在完成时里面的。

which修饰非限定性定语从句，前面必须出现介词或者都好，否则用that!

D中 found in Puerto Rico in 1991修饰前面的sloth!