DIRECTIONS Each passage below is accompanied by a number of questions. For som...
Each passage below is accompanied by a number of questions. For some questions, you will consider how the passage might be revised to improve the expression of ideas. For other questions, you will consider how the passage might be edited to correct errors in sentence structure, usage, or punctuation. A passage or a question may be accompanied by one or more graphics (such as a table or graph) that you will consider as you make revising and editing decisions.
Some questions will direct you to an underlined portion of a passage. Other questions will direct you to a location in a passage or ask you to think about the passage as a whole. After reading each passage, choose the answer to each question that most effectively improves the quality of writing in the passage or that makes the passage conform to the conventions of standard written English. Many questions include a “NO CHANGE” option. Choose that option if you think the best choice is to leave the relevant portion of the passage as it is.
A total of 11 questions are based on the following passage.
Paleontologists are using modern technology to gain a greater understanding of the distant past. With the aid of computed tomography (CT) scanning and 3-D printing, researchers are able to create accurate models of prehistoric fossils. [Q1] These models have expanded researchers’ knowledge of ancient species and [Q2] swear to advance the field of paleontology in the years to come.
CT scanners use X-rays to map the surface of a fossil in minute detail, recording as many as one million data points to create a digital blueprint. A 3-D printer then builds a polymer model based on this blueprint, much as a regular computer printer reproduces digital documents on paper. [Q3] Whereas the head of an ordinary computer printer moves back and forth while printing ink onto paper, the corresponding part of a 3-D printer moves in multiple dimensions while squirting out thin layers of melted polymer plastic. The plastic hardens quickly, [Q4] it allows the printer to build the layers of the final model. Compared with older ways of modeling fossils, scanning and printing in this way is extremely versatile.
 One significant benefit of 3-D printing technology is its ability to create scale reproductions of fossils.  But now 3-D scale models can be rearranged with ease, which is a huge boon to scientists.  A team led by Drexel University professor Kenneth Lacovara is making models of dinosaur bones one-tenth the bones’ original sizes [Q5] in order to learn how they fit together when the animals were alive.  In the past, such research was limited by the weight and bulk of the fossils as well as [Q6] its preciousness and fragility.  In many cases, scientists had to rearrange bones virtually, using artists’ renderings. [Q7]
Because CT scanners can map objects that are impossible to excavate, CT scanning and 3-D printing can also be used to reproduce fossils that scientists cannot observe firsthand. [Q8] By contrast, researchers from the National Museum of Brazil [Q9] has relied on this technique to study a fossilized skeleton that was discovered protruding from a rock at an old São Paulo railroad site. [Q10] The fossil was too delicate to be removed from the rock. Because of the fossil’s delicate nature, the team dug up a block of stone around the fossil and brought it to their lab. With the aid of a CT scanner and a 3-D printer, they were able to produce a resin model of the fossil. Examining the model, the researchers determined that [Q11] one had found a new species, a 75-million-year-old crocodile. While not every discovery will be as dramatic as this one, paleontologists anticipate further expanding their knowledge of ancient life-forms as CT scanning and 3-D printing continue to make fossils more accessible.
What will be the most pertinent answer to Q4?
The correct answer is C.
Choice C is the best answer because the relative pronoun “which” appropriately follows the independent clause “The plastic hardens quickly.” It introduces the relative clause explaining what the fact that the plastic hardens quickly allows the printer to do.
Choices A, B, and D are incorrect because each results in a comma splice (the joining of two independent clauses with only a comma).
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