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Since Brooke must meet on Sunday, and Carina and David want their lessons on the same day, their lessons must both be scheduled on Monday or both on Tuesday. The correct answer is (D).

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Correct Answer: C
Firm management believes that flex-time will help meet three goals: (1) decrease total costs (2) increase productivity (3) improve product quality. If the firm's research work requires considerable in-person collaboration, three hours a day of time together will not be sufficient and the firm's plan will lead to decreases in productivity and product quality. This will weaken the management's argument since its plan will not achieve two of its three goals.
A. The presence of new costs associated with flex-time does not weaken the argument that flex-time will decrease total cost as it may well be the case that cost savings outweigh cost increases. In other words, this answer only deals with one side of the equation (cost increases) and not the other side (cost decreases). Consequently, the answer does not enable us to conclude that the argument is weakened since it is entirely possible that on balance, costs will be reduced.
B. Since the firm abandoned it for "unknown reasons," we cannot make a conclusion about the affect of flex-time on costs, productivity, and product quality. It is entirely possible that the competitor abandoned flex-time for reasons not related to these three reasons and, therefore, for reasons not relevant to the argument of the management of the boutique research firm.
C. Since the firm in question performs work that requires frequent and in-person collaboration, it is reasonable to infer that cutting the time spent together at work down from 9 to 3 hours will have a considerable affect on productivity and quality as workers will have severely restricted access to a crucial component of their work (i.e., co-workers)

D. This answer strengthens the argument instead of weakening it. Further, using one employee's situation as an example is not the best grounds to critique an argument. 

E. The duration of the project (in and of itself) has nothing to do with costs, productivity, or product quality. Given the information in the question and in this answer, an argument could be made that flex-time will increase quality (employees enjoy their work more with flex-time and work harder).

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 Correct Answer: E
Due to the question being asked, the correct answer must follow closely from the statements in the stimulus. An answer that intuitively appears correct yet fails to follow closely from the statements in the stimulus is incorrect.
A. This answer snags a significant number of test takers. However, it is wrong because it draws too broad of a conclusion. The stimulus never indicates that "all" wavelengths that damage the eyes of animals are blocked by a healthy ozone layer. Further, notice the words "which enables more." The word "more" seems to indicate that a healthy ozone enables some wavelengths to pass through.
B. The fact that the decay in the ozone layer is believed to cause permanent eye damage in some animals does not mean other animals do not experience damage. Similarly, a decay of the ozone layer does not mean that wavelengths are entirely unfiltered. It simply means that less filtering of light exists.
C. The location of the animals that are damaged is never discussed and has no relevancy on the issue at hand.
D. Although this statement is true, it is not the main (or even a main) point of the argument. Similarly, the word "severe" is too strong and not supported by the statements in the stimulus.
E. This statement captures the main argument from the stimulus. Further, it is a near rephrase of "which enables some harmful wavelengths of light to reach the earth's surface."

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Correct Answer: E
The paradox: Northern Canada is quite cold and yet skeletal remains show evidence of experiencing very hot temperatures. This paradox could be explained by finding evidence that fires regularly occurred that would have subjected the bones to excruciatingly hot temperatures. If evidence existed that early humans from this time period hunted animals and started fires (implicitly for the purpose of cooking the animals—thereby creating skeletons of animals that experienced hot temperatures), a large step in explaining the paradox would be taken.
A. Unraveling the paradox depends on providing an explanation of how the skeletal remains experienced such hot temperatures yet this answer only heightens the paradox as it provides evidence that the skeletons' environment was much colder (not warmer) many years ago.
B. Although this provides an explanation of how "exactly one north Canadian species'" skeletons showed evidence of exposure to hot temperatures, it fails to account for why "many species from differing biological families [that] spanned about two thousand years showed" the same evidence of exposure to hot temperatures.
C. This answer provides an explanation for skeletons showing evidence of experiencing hot temperatures.
However, this answer does not explain why this evidence appeared among skeletons whose date "spanned about two thousand years." Further, the fire occurred "a little over 103,000 years ago" while the original argument makes clear that some of the skeletons which showed evidence of experiencing hot temperatures dated after this fire (i.e., the skeletons were from 100,000 years ago and "spanned about two thousand years" while the fire occurred "over 103,000 years ago").
D. The paradox exists in skeletons dating back to 100,000 years ago. Consequently, explaining how a fire (and thus hot temperatures) could have existed "as early as 70,000 years ago" does not explain the paradox. In other
words, this answer does not explain how the skeletons of animals 100,000 years old experienced hot temperatures (although it would explain how skeletons 70,000 years old experienced hot temperatures).
E. While this answer does not prove what caused the chared skeletal remains, it "best explains" how the skeletons experienced hot temperatures (i.e., the hunters cut wood and, implied in this, they started fires to cook animals).

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Correct Answer: E
The yield at a central Californian farm dropped significantly after 6 years of consistent growth. Clearly, something of importance to the yield changed. Some possibilities include: (1) a storm decimated the crop (although this level of storm could have only hit this year, as the crops grew "consistently and considerably over the past six years") (2) the farmer stopped using the technique (3) over a
period of six years, the technique overused natural soil nutrients and drained important chemicals that the farm crops needed to grow.
A. The original argument pertains to a decline in the yield of the farm, not a decline in the buyers. The farm's yield has no relationship with the number of buyers as yield simply refers to the ratio of seeds planted to crops available for harvest.
B. Although this confirms that the drop the farm in central California experienced is not unique, it does not explain the drop in yield.
C. Since a drought occurred 9 years ago prior to the experimental system and during the experimental system (3 years ago) without any affect on yields, it is not logical to conclude that the drought caused the decline in yields this year. In other words, since the yield grew "consistently" even during the drought 3 years ago and 6 years ago, it is illogical to conclude that the drought caused the decline in yield this year.
D. The circumstances between the two experimental systems are too different to allow comparisons and a logical deduction that the errors of the Iowa system explain the errors of the central California system. Specifically: (1) the length of time before declines in yields occurred differed considerably (2) the crops the farm produced differed (3) the geographic region of the farm (and climate) differed considerably.
E. The sustained (6 years, "consistently") and significant ("considerably") expansion in productivity ("yield") led to exhaustion of nutrients, meaning crops could not attain the chemical compounds they needed to grow. This answer explains why the crop yield dropped after so many years and why it dropped after years of growth.