Concept tested: Idioms, SV agreement
Difficulty Level: Moderate
Illustration: “Rock samples” is the subject for the verb “has been dated”. Rock samples must take a plural verb.
So A and B can be instantly eliminated.
Dated at is the correct idiomatic construction.
So C and D are also eliminated
E is the correct answer choice

Tip: Though “dated at” is preferred to “dated to be”, the same construction is not necessarily true for “estimated at” and “estimated to be” construction.
“Estimated at” should be followed by a noun because “at” is a preposition.
E.g: The molten iron is estimated at 1500 degrees Celsius.
“Estimated to be” generally follows phrases
E.g: The fossil is estimated to be 1000 years old.

This is NOT a specific English rule, but the way GMAT wants things to be
Support is given by:
In OG 12, Q 27 of SC, it says that the correct idiom is "estimated to be".
However this question appears in gmatprep
"With surface temperatures estimated at minus 230 degrees Farenheit, Jupiter's moon Europa has long been considered far too cold to support life, and with 60 square miles of water though to be frozen from top to bottom."

We can see from the non underlined part that "estimated at" is also as correct idiom.
Takeaway: Same rules do not apply to "estimated to be" and "dated to be"
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Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.47 billion years old and thus is evidence of the earliest known asteroid impact on Earth.

(A) has been dated to be 3.47 billion years old and thus is
(B) has been dated at 3.47 billion years old and thus
(C) have been dated to be 3.47 billion years old and thus are
(D) have been dated as being 3.47 billion years old and thus
(E) have been dated at 3.47 billion years old and thus are ANSWER

The subject 'rock samples' is plural so both the verb after 'dinosaurs', 'have', and the verb before 'evidence', 'are', have to be plural.

The correct idiom is 'dated at.'

Hope that helps .
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As rightly written by @Archillees - SV Agreement error >

Also to note is Difference between C and E
C uses subjunctive form - "to be" which is not required here.
E uses correct idiom "dated at"

Hey,
"to be" is neither used as a command subjunctive nor used as a hypothetical subjunctive.
For them you need special command verbs like demand, order, require etc.
They are popularly known as "bossy verbs"
Hypothetical subjunctive, as the name suggests, uses hypothetical constructions such as "were", "would" etc.

Souvik
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Hi,

Note that the highlighted portion doesn’t entirely consist of a single modifier.

I suggest you analyze the sentence structure to understand the role played by each element.

• Rock samples taken from the remains of an asteroid about twice the size of the 6-mile-wide asteroid

o that eradicated the dinosaurs
• has been dated to be 3.47 billion years old and
• thus is evidence of the earliest known asteroid impact on Earth.

The highlighted modifier presents a comparison with another “asteroid”.

So it would be logical to presume that the entire modifier is modifying “asteroid”, not “remains”.

Since this modifier is used to modify a noun, we can call it a “Noun Modifier”.

Observe that the modifier is in the non-underlined portion of the official sentence and so it should be correct as such.

Of course, enclosing it in a comma pair won’t make it incorrect. However, it would be unnecessary.

Hope this helps!

Regards,
Krishna
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Dear daysandhours,
I'm happy to respond.

The idiom "dated at" is 100% correct and favored by the GMAT, whereas "dated to be" is awkward and unidiomatic. I discuss this in this blog:
https://magoosh.com/gmat/2013/gmat-prep ... potpourri/

You may find helpful our free GMAT Idiom ebook:
https://magoosh.com/gmat/2013/gmat-idiom-ebook/
This information is also available in free Flash Card form:
https://gmat.magoosh.com/flashcards/idioms

Does all this make sense?
Mike
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Hi! estimated to be and dated at are both separate and correct idioms.
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ANSWER IS E

EXPLANATION :-
1) dated at is the correct idiom

2) the subject of the sentence is "rock samples" therefore SV agreement dictates that we use "Have". "Has" is incorrect

only E uses both "dated at" and "have"


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Hi Experts,

Could you please provide your comments for option C and option E.

Dated to be vs Dated at

Thanks

First Glance

The underline starts with the verb has; other answers start with have, so look for subject-verb issues.

Issues

(1) Subject-Verb; has; is

In the original sentence, the subject is the plural rock samples and the verb is the singular has been dated. Mismatch!

A plural subject needs a plural verb; eliminate answers (A) & (B), which both use the singular has. It turns out that the sentence also contains a second verb that goes with the same plural subject: is. Only answer (A) contains this error. The remaining answer use either the plural are or eliminate the verb entirely. (Remember that split for later.)

(2) Idiom: dated to be; dated as being

If you know the correct idiom, you might spot the error in the original sentence. If you don't, a vertical scan reveals that the answers offer three different options: dated to be, dated at, or dated as being.

The correct idiom for estimating the age of something is dated at a certain age. Eliminate answers (A), (C), and (D).

(3) Structure

Tackle the are versus nothing split mentioned in the subject-verb discussion above. (Remember that you already eliminated answer (A) for using is.)

(B), (D): Rock samples have been dated and thus evidence
(C), (E): Rock samples have been dated and thus are evidence

The and creates a parallel construction. Answers (B) and (D) are missing the needed verb are and are therefore sentence fragments; eliminate them

The Correct Answer

Correct answer (E) changes both verbs to the plural form to match the plural subject rock samples. Further, this choice uses the correct idiom, dated at a certain age.

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