TT gwd 31-28 -- C or E? NN plz help

chamcham

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28. GWD31-Q28

 

Rock samples taken from the remains of an asteroid about twice

the size of the 6-nuke-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

it should be "dated to be" or "dated at"? also it is "3.47 billion years old", which is adj., so is C better in this case?

Thx

chamcham

any help plz?

Zeldaw

you are right, it should be "dated to be". so C

chamcham

the only confused part is one gwd question:

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GWD-8-Q34: GWD-13-28

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

All the options are "dated at".

And also, I do see examples from nytime for both "dated at" and "dated to be", but seems "dated to be" only followed by something like "from accient time", etc. And I did see examples for "dated at 3 million years old" but still feel weired about "at + adj." ( prep. + adj.?). possibly some explaination whether this is legal?

thx,