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I submit that impact of solid bodies is the most fundamental of all interstellar processes that have taken place on the terrestrial planets: without impact, Earth, Mars, Venus, and Mercury would not exist.

Simply put, the collision of smaller objects is the process by which the terrestrial planets were born. On the surface, that the geological record of the earliest history of impacts on the terrestrial planets has been lost, is troubling. As the process is self-erasing, to a certain extent, the earliest record would have been lost even if processes of melting and internal evolution of the planets had not occurred. But much of the record of the last stages of accretion of the planets is preserved, especially on the moon, Mercury, and Mars. In fact, the last stage of accretion is still going on, albeit at a very slow rate.

This is fortunate, because we can study many aspects of the processes of planetary birth by investigation of the nature of small bodies that still exist, the dynamics of their orbital evolution, and the effects that they produce when they ultimately collide with a planet. If impact and accretion were not still occurring, it would be hard to come to grips with a number of difficult problems of planetary origin and early evolution.
It can be most reasonably inferred that which of the following accounts for the lack of a geological record concerning the history of impacts on the planets?
Sleep-learning experiments are notoriously difficult to conduct. For one thing, one must be sure that the subjects are actually asleep and stay that way during the "lessons." The most rigorous trials of verbal sleep learning have failed to show any new knowledge taking root. While more and more research has demonstrated the importance of sleep for learning and memory consolidation, none had managed to show actual learning of new information taking place in an adult brain during sleep.

Recently, however, researchers chose to experiment with a type of conditioning that involves exposing subjects to a tone followed by an odor, so that they soon exhibit a similar response to the tone as they would to the odor. The pairing of tones and odors presented several advantages. Neither wakes the sleeper (in fact, certain odors can promote sound sleep), yet the brain processes them and even reacts during slumber. Moreover, the sense of smell holds a unique non-verbal measure that can be observed -- namely sniffing. The researchers found that, in the case of smelling, the sleeping brain acts much as it does when awake: We inhale deeply when we smell a pleasant aroma but stop our inhalation short when assaulted by a bad smell. This variation in sniffing could be recorded whether the subjects were asleep or awake. Finally, this type of conditioning, while it may appear to be quite simple, is associated with some higher brain areas -- including the hippocampus, which is involved in memory formation.

In the experiments, the subjects slept in a special lab while their sleep state was continuously monitored. As they slept, a tone was played, followed by an odor -- either pleasant or unpleasant. Then another tone was played, followed by an odor at the opposite end of the pleasantness scale. Over the course of the night, the associations were partially reinforced, so that the subject was exposed to just the tones as well. The sleeping volunteers reacted to the tones alone as if the associated odor were still present -- by either sniffing deeply or taking shallow breaths. The next day, the now awake subjects again heard the tones alone -- with no accompanying odor. Although they had no conscious recollection of listening to them during the night, their breathing patterns told a different story. When exposed to tones that had been paired with pleasant odors, they sniffed deeply, while the second tones -- those associated with bad smells -- provoked short, shallow sniffs.

The team then asked whether this type of learning is tied to a particular phase of sleep. In a second experiment, they divided the sleep cycles into rapid eye movement (REM) and non-REM sleep, and then induced the conditioning during only one phase or the other. Surprisingly, they found that the learned response was more pronounced during the REM phase, but the transfer of the association from sleep to waking was evident only when learning took place during the non-REM phase. The researchers suggest that during REM sleep we may be more open to influence from the stimuli in our surroundings, but so-called "dream amnesia" -- which makes us forget most of our dreams -- may operate on any conditioning occurring in that stage of sleep. In contrast, non-REM sleep is the phase that is important for memory consolidation, so it might also play a role in this form of "sleep-learning.
The first paragraph serves primarily to
Due to an easing of state sanctions against hunting, Deersdale Preserve has experienced an influx of hunters in the last several months. During this time, the silvertail fox, a popular target for hunters, has seen a marked decrease in population. Therefore, to prevent the population of silvertail fox-an important apex predator responsible for keeping the Deersdale County`s rabbit population in check-from falling even lower, the state should once again place strict sanctions against hunting.
Which of the following, if true, may suggest that stricter sanctions against hunting would not have the desired effect?
Pediatrician: Child psychologists recommend that mothers of one-year olds not only name objects in the immediate environment, but that they include the color of the object, when applicable. For instance, if a mother hands her child a red ball, she should say,"This is a red ball."Nonetheless, even if mothers began to name the color, instead of simply saying,"This is a ball,"no real benefit will be conferred to the child, because studies have shown that children under 18-months old do not grasp the notion of color.
The pediatrician's argument is most vulnerable to which of the following?
The Canadian elk has traditionally been limited in its geographic range by the presence of elderberries, its primary source of food, which only grow up until a certain point in the tundra. A recent rise in temperatures, however, has seen a spread in the growth of elderberries northwards into the tundra. Therefore, the overall range of the Canadian elk can be expected to increase.
Which of the following, if true, best casts doubt on the argument?
In the last few years, a drastic spike in sea temperatures around Prudhoe Bay has caused the eggs of snow crabs to hatch earlier in the year than they had previously. As a result, baby snow crabs are more likely to be caught by deep sea fishing boats, since deep sea fishing boats are more numerous in Arctic waters during the fall season than they are during the winter season.
Which of the following pieces of information is necessary to evaluate the argument?
In a freshman biochemistry class at Newton University, the teacher assigns the class only `A`s,`B`s`or`C`s.The average on the semester final for the class of 2012 was five points lower than that of the class of 2011. Therefore, the percent of students who received`C`s was greater in 2012 than in 2011.
Which of the following, if true, suggests the conclusion above is not necessarily valid?
Nutritionist: Multivitamins are potent storehouses of antioxidants, substances that fight the oxidation process, which breaks down the body. Nonetheless, according to longitudinal studies-studies that follow subjects over the course of many years-those who take multivitamins every day have a decreased longevity. Clearly, if people want to live longer they should avoid antioxidants.
Which of the following is an assumption the argument relies on?
Language acquisition has long been thought of as a process of imitation and reinforcement. Children learn to speak, in the popular view, by copying the utterances heard around them, and by having their response strengthened by the repetitions, corrections, and other reactions that adults provide. In recent years, it has become clear that this principle will not explain all the facts of language development. Children do imitate a great deal, especially in learning sounds and vocabulary; but little of their grammatical ability can be explained in this way. Two kinds of evidence are commonly used in support of this criticism – one based on the kind of language children produce, the other on what they do not produce.

The first piece of evidence derives from the way children handle irregular grammatical patterns. When they encounter such irregular past-tense forms as went and took or such plural forms as mice and sheep, there is a stage when they replace these by forms based on the regular patterns of the language. They say such things as wented, taked, mices, mouses, and sheeps. Evidently, children assume that grammatical usage is regular, and try to work out for themselves what the forms `ought` to be – a reasoning process known as analogy. They could not have learned these forms by a process of imitation. The other kind of evidence is based on the way children seem unable to imitate adult grammatical constructions exactly, even when invited to do so.
According to the passage, children cannot learn from a process of imitation alone for which of the following reasons?
The idea that all mental functions are derived from the brain originated with Hippocrates, but it was largely neglected until the late 18th century, when Franz Gall attempted to link psychology and brain science. Gall took advantage of what was already known about the cerebral cortex. He was aware that it was bilaterally symmetrical and subdivided into four lobes. However, he found that these four lobes were, by themselves, inadequate to account for the forty-odd distinct psychological functions that psychologists had characterized by 1790. As a result he began to analyze the heads of hundreds of musicians, actors, etc., relating certain bony elevations or depressions under the scalp to the predominant talent or defects of their owners. Based on his skull palpitation, Gall subdivided the cortex into roughly forty regions, each of which served as an organ for a specific mental function.

While Gall`s theory that all mental processes derive from the brain proved to be correct, his methods for localizing specific functions were deeply flawed because they were not based on what we would now consider valid evidence. Gall did not test his ideas empirically by performing autopsies on the brains of patients and correlating damage to specific regions with defects in mental attributes; he distrusted the diseased brain and did not think it could reveal anything about normal behavior. Instead, he developed the notion that as each mental function is used, the particular area of the brain responsible for that function becomes enlarged. Eventually, a given area may become so bulky that it pushes out against the skull and produces a bump on the head.
Which of the following is NOT an assumption that Gall makes regarding the relation between a person`s aptitude and personality traits, and that person`s brain?

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