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
>> Remove the modifiers and see what is left: "Fossils of the arm of a sloth..made it the earliest known mammal..." - reject
(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
>> Remove the modifiers and see what is left: "Fossils of the arm of a sloth..has been dated at 34mn years..." - is fine so keep it.
(C) sloth that was found in Puerto Rico in 1991, was dated at 34 million years old, making this the earliest known mammal of
>> Remove the modifiers and see what is left: "Fossils of the arm of a sloth..was dated at 34mn years..." - is fine so keep it
(D) sloth, found in Puerto Rico in 1991, have been dated at 34 million years old, making the sloth the earliest known mammal on
>> Remove the modifiers and see what is left: "Fossils of the arm of a sloth..have been dated at 34mn years"
(E) sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliest known mammal of
>> Remove the modifiers and see what is left: "Fossils of the arm of a sloth..was dated at 34mn years"
The second question to ask: is there SVA? For that, we need to ask what is being dated? The sloth or the fossils? It has to be the latter so we can:
Eliminate B,C,E
Now let us compare A and D:
Were the fossils the oldest living mammal or the sloth? It is the sloth - so whenever you see 2 answer options where one of them replaces the pronoun with the right noun - there is a very good chance you are looking at pronoun ambiguity.
Therefore, D
Here, we have an “ing” modifier functioning as an adverbial.
“making the sloth the earliest known mammal on..” IS MODIFYING THE ENTIRE PRECEDING CLAUSE -“The fossils of the arm of the sloth found in Puerto Rico in 1991, have been dated at 34 million years old”