영어 모의고사 (자동 편성)

Time blocking is a time-management technique in which a person ①divides the day into fixed blocks. Each block is then assigned to a single task. Instead of relying on a loose to-do list, the person decides exactly when each task ②will starting and end. This approach lowers the mental effort of deciding what to do next, since the schedule already provides the answer. It also limits multitasking, because each block ③is reserved for only one activity at a time. For instance, a student may block ninety minutes for math practice, ④leaving no room for messages or web browsing. Because each block has a clear boundary, unfinished work is ⑤less likely to quietly spread into the next task.

Athletes preparing for major endurance events sometimes ① trains 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, ② which carry oxygen more efficiently through the bloodstream to working muscles. When these athletes return to sea level, where oxygen is more abundant, their blood ③ retains 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 ④ undermines 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 ⑤ to maintain quality and intensity.

Sleep debt refers to the cumulative gap between the amount of sleep a person needs and the amount they actually get. Unlike a financial debt, however, this deficit cannot simply ① be repaid with a single long weekend of rest. When someone loses two hours of sleep every night for a week, the body does not treat the shortage as fourteen separate small losses; instead, it accumulates the deficit, and the resulting impairment in attention and mood can resemble that of a person ② who has been awake for an entire night. Researchers have found that even modest, chronic sleep restriction gradually impairs reaction time and decision-making, often without the affected person ③ noticing the decline. This is because subjective feelings of tiredness tend to plateau after a few days, even as objective performance keeps ④ deteriorate. Consequently, people frequently underestimate how much sleep debt they are carrying until a demanding task suddenly ⑤ exposes the accumulated cost.

When the body fights off an infection, the immune system relies heavily on adequate sleep to function ① effectively. During deep sleep, the body produces and releases cytokines, proteins that help ② regulate immune responses and coordinate the fight against harmful invaders. People who consistently sleep fewer than six hours a night show measurably ③ weaker antibody responses after vaccination compared with those who sleep seven or eight hours. Chronic sleep deprivation also appears to ④ reduce low-grade inflammation throughout the body, a state that has been linked to a higher risk of heart disease. Rather than being a passive state, sleep functions as an active period during which the immune system repairs itself and ⑤ prepares for future threats.

For centuries, dreams have ① fascinated scientists and philosophers alike, yet no single theory fully explains why the sleeping brain generates such vivid and often bizarre experiences. One prominent idea suggests that dreaming helps the brain process emotional experiences, replaying difficult events in a ② safe, low-stakes environment so that their emotional intensity gradually fades. Another theory proposes that dreams serve a more practical function, allowing the brain to ③ ignore responses to threats without any real danger, a kind of nightly simulation that may have offered early humans a survival advantage. Still other researchers argue that dreaming is simply a byproduct of the brain organizing memories, with vivid imagery arising as the mind sorts through the day's ④ information rather than serving any independent purpose of its own. Because these theories rest on indirect evidence, none has been ⑤ conclusively proven.

Melatonin is a hormone produced by a small gland deep within the brain, and its release follows a remarkably predictable daily pattern. 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. 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. Unlike some hormones that directly cause the body to perform a task, _______________, 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. This schedule assumes that teenagers can simply go to bed earlier to compensate, but biology tells a different story. During adolescence, the body's internal clock shifts later, delaying the release of melatonin until well after ten at night. As a result, most teenagers are not physiologically ready to fall asleep until much later than younger children or adults. When early start times force them to wake before their bodies have completed a full sleep cycle, the mismatch accumulates into a chronic sleep debt that affects concentration and mood throughout the school day. Researchers who study this mismatch argue that _______________. Some school districts that delayed their start times by thirty minutes reported improvements in attendance, suggesting that the timing of the school day matters more than commonly assumed.

During sleep, the brain does not simply rest; it actively reorganizes the day's experiences into lasting memories through a process called consolidation. Newly formed memories are initially fragile and stored primarily in a brain region called the hippocampus, which has limited long-term capacity. While a person sleeps, particularly during the deep stages of non-REM sleep, neural activity replays these fresh memory traces in rapid, compressed sequences, gradually transferring the information to the cortex for more durable, long-term storage. This replay strengthens the connections between neurons that encoded the original experience, making the memory more resistant to interference from unrelated events the following day. Sleep researchers have demonstrated this effect experimentally: participants who slept after learning a list of word pairs recalled more items the next day than participants who remained awake instead. Crucially, the benefit was not limited to simple recall; sleep also seemed to help participants extract general patterns from the material, suggesting that _______________.

Wearable devices that track sleep have become enormously popular, promising a detailed breakdown of light, deep, and REM sleep each night. (A) Despite these limitations, many users have come to treat the nightly score generated by their device as an objective medical verdict, sometimes experiencing anxiety when the number falls below what they expect, a phenomenon researchers have begun calling orthosomnia. (B) Independent studies comparing wearable data with polysomnography, the gold-standard method used in clinical sleep labs, have found that consumer devices are reasonably accurate at distinguishing sleep from wakefulness but considerably less reliable at identifying specific sleep stages. Some trackers overestimate deep sleep, while others underestimate the amount of time spent in REM sleep, and the margin of error can vary widely between brands. (C) These gadgets typically rely on movement sensors and heart rate monitors to estimate sleep stages, since directly measuring brain activity would require equipment found only in a sleep laboratory. This indirect approach, however, introduces significant uncertainty.

Not all environmental changes happen at the same steady pace. (A) A well-known example involves melting Arctic ice, which exposes darker ocean water that absorbs more sunlight and speeds up further melting in a self-reinforcing cycle. (B) Once this kind of threshold is crossed, reversing the damage becomes extremely difficult, which is why scientists consider identifying these points an urgent priority. (C) Some changes accumulate slowly and predictably, while others can suddenly accelerate once a critical threshold, known as a tipping point, is crossed.