TomB wrote:
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
First GlanceThe underline starts with the verb
has; other answers start with
have, so look for subject-verb issues.
Issues(1) Subject-Verb; has; isIn 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 beingIf 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) StructureTackle 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 AnswerCorrect 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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