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.
(This question is from Official Guide. Therefore, because of copyrights, the complete question cannot be copied here. The question can be accessed at GMAT Club)
The sentence talks about fossils of the arm of a sloth. Then, we encounter ‘verb-ed’ form. Is it a modifier or a verb? We know the subject is “Fossils”, and it doesn’t make sense to say ‘fossils found something’. So, ‘found’ is not a ‘verb’ and thus is a modifier. But what is it modifying? Is it modifying sloth or arm or fossils? At this point, it might be hard to choose one thing over the other.
As we read further, we encounter another ‘verb-ed’ preceded by a ‘and’, so we understand that ‘dated’ is in a list with ‘found’. Thus, ‘dated’ must be modifying the same entity as ‘found’. Now, we know that it makes much more logical sense to say that the fossils were dated at 34 million years than to say that the arm or the sloth was dated at 34 million years. So, by this reasoning, we figure out that both ‘found’ and ‘dated’ are modifying ‘Fossils’.
The sentence then presents another verb-ed ‘made’. Now, ‘made’ is not in a list with the other two verb-ed modifiers. We see that ‘made’ is the main verb of the sentence. The sentence essentially says that these fossils made the sloth the earliest known mammal of some islands.
There are two problems in the sentence:
- The sentence says ‘fossils made the sloth the earliest known mammal’. It doesn’t make a lot of logical sense to say that fossils did something!
- The antecedent for ‘it’ is not structurally clear. Logically, we know that ‘it’ should refer to ‘the sloth’. However, structurally, ‘the sloth’ is deep inside the prepositional phrase modifying ‘fossils’. Thus, it is difficult to figure out the antecedent for ‘it’ from the structure of the sentence.
Please note that both the above errors are not deterministic i.e. you shouldn’t reject an option based on the two. Hold them against the option and wait for a better option, but at the same time, if you don’t find a better option, be open to come back and select this option.
(A) Incorrect. There is indeed a better option, as we’ll find 🙂
(B) Incorrect. For the following reasons:
- ‘they’ has no antecedent.
- Singular verb ‘has been dated’ for plural subject ‘fossils’.
- Problem no. 2 of the original sentence
(C) Incorrect. For the following reasons:
- Singular verbs “was found” and “was dated” for plural subject “fossils”
- The antecedent of “this” is not clear. Also, ‘this’ is demonstrative pronoun, meaning that it should always be used with a noun e.g. this animal, this book, (or in plural) these objects etc.
(D) Correct. Both the errors in the original sentence have been corrected. “making the sloth the earliest…” is a clause modifier, presenting the result of the preceding clause. Please note that verb-ing ‘making’ doesn’t make a lot of sense with the subject of the preceding clause ‘fossils’, as was pointed out in the sentence analysis. However, since the verb-ing clearly expresses the result of the preceding clause, this ‘not-making-sense-with-the-subject’ is allowed (sometimes, it is allowed).
(E) Incorrect. For the following reasons:
- Singular verb “was dated” for the plural noun “fossils”
- Problem no. 1 of the original sentence
- The awkward structure: “which, found, was dated”. When we know both ‘found in…” and “dated at…” present additional information about ‘fossils’, why not make them parallel and thus easier to read rather than make a mess out of them as in the present option.