Bunuel
12 Days of Christmas GMAT Competition with Lots of FunThe ancient Olympic games were held every four years, a period of time known as an Olympiad;
usage of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, who was chief librarian at the Library of Alexandria and is known for his calculation of the circumference of the Earth and for the Earth’s axial tilt as well as for his introduction of the sieve of Eratosthenes, an ancient algorithm for finding prime numbers.
(A) usage of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, who was chief librarian at the Library of Alexandria and is known for his calculation of the circumference of the Earth and for
(B) the use of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, who was chief librarian at the Library of Alexandria and is known for his calculation of the circumference of the Earth and
(C) the use of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, chief librarian at the Library of Alexandria, known for his calculation of the circumference of the Earth and of
(D) usage of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, who was chief librarian at the Library of Alexandria and known for his calculation of the circumference of the Earth and
(E) the use of an Olympiad as a unit of time in ancient histories is sometimes credited to Eratosthenes, who was chief librarian at the Library of Alexandria and is known for his calculation of the circumference of the Earth and for
Manhattan Prep Official ExplanationFirst Glance: Differences in the answer choices provide clues about what a problem might be testing. Before reading the sentence, glance at the beginning of the underline and down the beginning (just the beginning!) of the five answer choices to look for one early clue as to what this sentence is testing.
The sheer length of the underlined portion indicates that Structure and Modifiers might be tested. Additionally, the underline begins just after a semicolon, indicating that Structure might be tested in this problem.
Issues: (1) Parallelism
Each answer choice contains several instances of the conjunction
and. These conjunctions and the idiom
as well as in the original sentence after the underline indicate parallelism. The first level of parallelism is a top-level description of Eratosthenes: He
was chief librarian, and
he is known for two accomplishments. Those two accomplishments are also meant to be parallel: He is known
for his calculations of (two things) and he is known
for his introduction of (another thing). Finally, there must be parallelism within the two calculations that he is known for: the calculation of the Earth’s circumference and the calculation of the Earths’ axial tilt.
In the original sentence, all of the levels of parallelism are correct except for the two calculations; He is known for his calculation
of the circumference of the Earth and
for the Earth’s axial tilt. The preposition
for doesn’t connect back to the calculation in the first half of the parallel structure (calculation
for the Earth’s axial tilt is illogical). Eliminate choices (A) and (E) for this parallelism issue.
Choice (C) creates a parallelism error. The description
chief librarian … , known for his calculation is structured as two parallel elements in a longer series of descriptions, but there is no final element in that series. Eliminate choice (C).
Choice (D) attempts parallelism between
who was chief librarian … and known for his calculation. Structurally, this would mean that Eratosthenes
was chief librarian … and (he was)
known for these accomplishments. However, this illogically implies that Eratosthenes is no longer known for these accomplishments. Eliminate choice (D).
The Correct Answer: Answer (B) removes the preposition
for from the end of the choice and correctly makes
for his calculation parallel to
for his introduction. Choice (B) also preserves the
comma who modifier that most clearly describes Eratosthenes:
who was chief librarian … and is known for these achievements.