gmat-31-28请教

28: 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 3.47billion 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

我选E

google了一下，dated to be ... years old和dated at ... years old都有，晕了

我比较倾向于dated to be，好像og有一道题是选的estimated to be

open to discuss...

14. Paleontologists believe that fragments of a primate
jawbone unearthed in Burma and estimated at 40 to 44 million years old provide evidence of a crucial step along the evolutionary path that led to human beings.

(A)at 40 to 44 million years old provide evidence of
(B)as being 40 to 44 million years old provides evidence of
(C)that it is 40 to 44 million years old provides evidence of what was
(D)to be 40 to 44 million years old provide evidence of
(E)as 40 to 44 million years old provides evidence of what was

D, the best choice, correctly follows estimated with to be. The other choices present structures that are not idiomatic when used in conjunction with estimated. Choices B, C, and E all mismatch the singular verb provides with its plural subject, fragments, and in choices C and E, what was is unnecessary and wordy. In choice C, the use of the verb phrase estimated that it is produces an ungrammatical sentence.

查了一下Longman，be estimated to be是fixed phrase，不够有说服力

继续讨论

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 (D)
   
5. sloth which, found in Puerto Rico in 1991, was dated at 34 million years old, made the sloth the earliest known mammal of

五个选项都是dated at，那这题是不是选E呢？？

dated to 追溯到 ....(年前),后面应该是多少年，不是多少岁。

dated at 3.47 billion years old 在多少岁时，确定了年代。

所以，还是E好些。