영어 모의고사 (자동 편성)

Many people struggling to fall asleep in noisy environments turn to white noise machines, devices that ①emit a steady, uniform sound covering a broad range of frequencies. The appeal lies in a phenomenon called auditory masking, in which a constant background sound makes sudden noises ②less noticeable to the sleeping brain. Without this masking effect, an abrupt change in sound is far more likely ③to trigger a brief awakening, even if the sleeper does not consciously remember it the next morning. Studies comparing sleep in quiet rooms with sleep alongside white noise have found that participants using white noise ④experienced fewer of these brief awakenings. However, researchers caution that the benefit depends heavily on volume and consistency, since noise that is too loud or that ⑤varying unpredictably can itself become a source of disruption rather than a remedy.

Athletes preparing for major endurance events sometimes ①trains for weeks at high altitude, where the air contains less oxygen than at sea level, in hopes of gaining a physiological edge once they return to compete at lower elevations. In this thin air, the body responds by producing more red blood cells, ②which carry oxygen more efficiently through the bloodstream to working muscles. When these athletes return to sea level, where oxygen is more abundant, their blood ③retains this elevated capacity for a limited period, potentially translating into improved endurance performance. However, the benefits of altitude training are far from guaranteed, since individual athletes respond quite differently to the same conditions, and some experience excessive fatigue that ④undermines the very training they hoped to complete. Many elite programs therefore follow a strategy known as live high, train low, in which athletes sleep at altitude to stimulate blood adaptations but perform intense workouts at lower elevation ⑤to maintain quality and intensity.

Smart speakers have quietly become a fixture in many households, responding to spoken requests for weather updates, music, or kitchen timers. Behind this ①simple exchange lies a complex process: the device converts sound waves into text, interprets the meaning using language models, and then generates a spoken reply, all within a second or two. Because these assistants ②improve by learning from millions of interactions, they gradually become better at recognizing regional accents and casual phrasing that once confused them. Still, the technology remains far from ③perfect. Background noise, overlapping voices, or an unusual sentence structure can cause the assistant to misunderstand a simple request, sometimes with ④flawless results. Engineers continue to refine these systems, but many admit that truly natural conversation remains one of the hardest ⑤goals in the entire field of artificial intelligence.

When a customer opens a company's website at midnight with a billing question, an actual employee is unlikely to be available, which is exactly the gap that customer service chatbots were built to fill. These programs can instantly answer common questions, track packages, and process simple refunds without making anyone wait on hold. Yet the technology has clear boundaries. When a customer's problem is unusual, emotionally charged, or simply does not fit the chatbot's script, _______________. Many companies have responded by designing chatbots to recognize their own limits, automatically transferring a frustrated customer to a human agent.

Ambitious young athletes and the parents who support them sometimes assume that more training automatically produces better results, a belief that occasionally leads to a condition known as overtraining syndrome. Unlike ordinary fatigue that resolves after a few days of rest, overtraining syndrome develops gradually over weeks or months of insufficient recovery relative to training load, eventually producing persistent exhaustion, declining performance despite continued hard work, and increased susceptibility to illness and injury. Warning signs are often subtle at first, including disrupted sleep, irritability, and a loss of enthusiasm for a sport the athlete once genuinely enjoyed, which adults often mistake for ordinary moodiness. Recovery from full-blown overtraining syndrome can take months rather than days, which is why _______________.

Melatonin is a hormone produced by a small gland deep within the brain, and its release follows a remarkably predictable daily pattern. (A) This rhythm is controlled primarily by light: specialized cells in the eye detect brightness and send signals that either permit or suppress melatonin production, which is why exposure to bright screens late at night can delay its release and make falling asleep more difficult. (B) Levels stay low throughout the bright hours of the day, begin rising in the evening as darkness falls, peak in the middle of the night, and then decline again as morning approaches. (C) Unlike some hormones that directly cause the body to perform a task, melatonin does not force sleep to occur; instead, it signals to the rest of the body that night has arrived, preparing various systems to shift into a lower-energy state. Because of this signaling role, taking melatonin supplements at the wrong time can shift a person's internal clock in the opposite direction from what was intended.

Across many countries, high schools begin classes early in the morning, often before eight o'clock. (A) Researchers who study this mismatch argue that the underlying problem is not laziness or poor discipline among students, but a scheduling system built around adult rhythms rather than adolescent ones. (B) This schedule assumes that teenagers can simply go to bed earlier to compensate, but biology tells a different story, because the body's internal clock shifts later during adolescence, delaying the release of melatonin until well after ten at night. (C) As a result, most teenagers are not physiologically ready to fall asleep until much later than adults, and when early start times force them to wake before completing a full sleep cycle, the mismatch accumulates into a chronic sleep debt.

After a viewer finishes an episode, a streaming service rarely leaves the choice of what to watch next entirely up to chance. (A) The system is not without drawbacks, however, since favoring titles similar to what a viewer already enjoys can quietly narrow someone's exposure to unfamiliar genres, directors, or cultures. (B) Instead, a recommendation algorithm compares that viewer's habits with patterns drawn from millions of other users, then ranks thousands of titles in order of predicted interest. (C) This approach keeps viewers engaged far longer than a simple list of new releases ever could, which is precisely why streaming companies invest so heavily in refining it.

Because the airway narrows gradually rather than closing all at once, the severity of each episode can vary widely. Sleep apnea is a disorder in which breathing repeatedly stops and restarts during sleep, often because the muscles at the back of the throat relax too much and block the airway. ( ① ) Each pause can last from a few seconds to over a minute, and it may occur dozens of times in a single night without the sleeper ever waking up fully. ( ② ) Because these interruptions rarely produce a clear memory the next morning, many people remain unaware that anything is wrong, even as chronic fatigue, headaches, and irritability build up over months. ( ③ ) Doctors therefore rely less on a patient's own account of the night and more on objective measurements, such as overnight oxygen levels and airflow patterns recorded in a sleep laboratory. ( ④ ) Left untreated, the disorder has been linked to serious long-term risks, including high blood pressure and heart disease, which makes an accurate diagnosis far more urgent than its subtle nighttime symptoms might suggest. ( ⑤ )

This is precisely why an experienced athlete returning after an injury often regains sharp form faster than a complete beginner ever could. Anyone who has ridden a bicycle after a decade away from one has likely experienced muscle memory firsthand: the body seems to recall a complex skill almost instantly, even when conscious memory of the exact movements has faded. ( ① ) Contrary to what the name suggests, muscles themselves do not actually store memories; the phenomenon originates in the brain and nervous system, where repeated practice gradually shifts control of a well-learned movement from regions associated with conscious thought to areas that operate largely automatically. ( ② ) This shift explains why a skilled athlete can execute a complicated sequence of movements without consciously thinking through each individual step, freeing mental attention for strategy and decision-making instead. ( ③ ) Interestingly, research also suggests that these neural pathways can remain partially intact even after long periods without practice, which is why relearning a skill is typically much faster than learning it for the very first time. ( ④ ) Coaches often exploit this principle by ensuring that fundamental techniques are practiced correctly from the very beginning. ( ⑤ )