Rock samples GMATprep question..

[rahulg83]

Rock samples taken from the remains of an asteroid about twice the size of a 6-mile-wide asteroid that eradicated the dinosaurs has been dated to be 3.7 billion years old and thus is evidence of earliest known asteroid impact on earth.

A) has been dated to be 3.7 billion years old and thus is

B) has been dated as 3.7 billion years old and thus

C) have been dated to be 3.7 billion years old and thus are

D) have been dated as being 3.7 billion years old and thus

E) have been dated at 3.7 billion years old and thus are

Please explain the reasoning

[tanviet]

samples are plural so require "have"

in D, there is no "are" at the end so D is wrong

between c and e, I do not remember idiom . "dated to be " or "dated at"

[hk]

2 mistakes:

1. If you know the idiom, you will be able to nail this question within 10 secs.

Its "Dated at..." and there is only one option. - E

2. Rock samples....... has been dated .... is wrong (Subj verb agreement)
It should be "Have been"

[rahulg83]

Hi hk,
Shouldn't it be like rock samples dated at 3000 years. I am confused by the additional 'old' here. I think it's better to write 'rock samples dated to be 3000 years old'. Well, this is a GMAC question, can't argue much, but i would like to know correct idiomatic usages of 'dated'.

[graghukalyan]

I second rahulg83.
I think when we use "dated at", we should specify a specific number as in year, place etc.

Ex : The first edition of the grammar is therefore now generally dated at 1745 (cf. Michael 1987:457).

IMO - C is a better choice. However, request someone to share some idiomatic usages of "dated"