영어 모의고사 (자동 편성)

After an especially demanding training session, the instinct to collapse onto a couch and remain motionless is understandable, yet exercise physiologists increasingly recommend the ①opposite approach. Active recovery involves performing low-intensity movement, such as a light jog, an easy swim, or a gentle bike ride, on days following intense exertion rather than resting completely. This gentle activity keeps blood circulating through tired muscles, which appears to help ②clear metabolic byproducts that accumulate during hard exercise more efficiently than complete stillness does. Some athletes worry that any movement at all will interfere with the repair process, but research suggests that truly light activity ③accelerates healing considerably and may even reduce the perceived soreness that follows a hard session. The key distinction lies entirely in ④intensity: active recovery is not a second workout in disguise but a deliberately gentle session designed to support, rather than compete with, the body's underlying repair ⑤mechanisms.

Melatonin is a hormone produced by a small gland deep within the brain, and its release follows a remarkably ①unpredictable 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 ②decline 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 ③delay its release and make falling asleep more difficult. 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 ④lower-energy state. Because of this signaling role, taking melatonin supplements at the wrong time can shift a person's internal clock in the ⑤opposite direction from what was intended.

Across the world, teenagers are chronically short on sleep, often getting two or three hours less than the eight to ten hours experts recommend for their age. Part of the problem lies in biology: as puberty begins, the body's internal clock naturally ①shifts later, making it difficult for teenagers to fall asleep before eleven at night. Yet school start times rarely adjust to this shift, forcing students to wake before their bodies are ready. The consequences extend well beyond simple tiredness. Chronic sleep loss during adolescence has been linked to ②impaired concentration, weakened memory, and a higher risk of anxiety and depression. It can also disrupt the hormones that regulate appetite, contributing to ③unhealthy weight gain over time. Some school districts have experimented with delaying start times by even thirty minutes, and early results suggest that students who gain that extra rest show ④worsened grades, better mood, and fewer tardy arrivals. Despite this evidence, changing entrenched school schedules remains a slow and ⑤contentious process.

Caffeine is the most widely consumed stimulant in the world, prized for its ability to ①sharpen focus and fight off fatigue within minutes of consumption. It works by blocking adenosine, a chemical that gradually builds up in the brain throughout the day and makes us feel ②decreasingly sleepy the longer we stay awake. By occupying the receptors that adenosine would normally bind to, caffeine tricks the brain into feeling alert even when the body has accumulated significant sleep pressure. The effects, however, last far longer than most people realize. Because caffeine can remain active in the bloodstream for five to six hours, a cup of coffee consumed in the late afternoon may still be ③interfering with the ability to fall asleep at midnight. Even when people do not consciously notice difficulty falling asleep, caffeine has been shown to ④reduce the amount of deep, restorative sleep obtained later in the night. For this reason, many sleep specialists advise ⑤avoiding caffeine after early afternoon.

Social psychologists describe a phenomenon called the bystander effect, in which individuals become less likely to help a victim as the number of witnesses increases. Each observer assumes someone else will step in, and this diffusion of responsibility leaves no one willing to act. Cyberbullying magnifies this problem, since a single humiliating post can be witnessed by thousands of people scattered across the internet rather than a few standing nearby. Anonymity intensifies the effect further, allowing silent observers to scroll past cruel comments without feeling accountable for their inaction. Some bystanders even worry that intervening publicly might make them the bully's next target, so they choose to remain silent instead. However, silence signals approval to both the bully and the audience watching the exchange unfold. Experts insist that even a single supportive comment can disrupt this harmful pattern. Therefore, witnesses online must _______________.

For centuries, dreams have fascinated scientists and philosophers alike, yet no single theory fully explains why the sleeping brain generates such vivid and often bizarre experiences. (A) Another theory proposes that dreams serve a more practical function, allowing the brain to rehearse responses to threats without any real danger, a kind of nightly simulation that may have offered early humans a survival advantage. (B) Still other researchers argue that dreaming is simply a byproduct of the brain organizing memories rather than serving any independent purpose, and because these theories rest on indirect evidence, none has been conclusively proven, leading many scientists to suspect that dreaming may serve several functions simultaneously. (C) One prominent idea suggests that dreaming helps the brain process emotional experiences, replaying difficult events in a safe, low-stakes environment so that their emotional intensity gradually fades.

Insomnia is rarely caused by a single factor; it usually emerges from an interaction between psychological stress and physiological arousal that keeps the body from settling into sleep. (A) At the same time, the body's stress response system can become chronically activated, releasing hormones such as cortisol that keep heart rate and body temperature elevated at night, both of which interfere with the natural drop in arousal needed to fall asleep. (B) Poor sleep habits, including irregular bedtimes and excessive screen use before bed, can further weaken the body's internal signals for sleep onset. Because these psychological and physiological factors reinforce one another, effective treatment for chronic insomnia addresses both the racing mind and the underlying pattern of physical tension, rather than relying on medication alone. (C) A common trigger is what researchers call cognitive hyperarousal, in which the mind continues to race with worries about work, relationships, or even the inability to sleep itself, creating a frustrating cycle where anxiety about insomnia becomes a cause of insomnia.

Sleep hygiene refers to a set of simple daily habits that help the body prepare for consistent, restorative rest. (A) They also advise reserving the bedroom for sleep alone, since using the bed to study, scroll through a phone, or watch videos teaches the brain to associate that space with wakeful activity rather than rest. (B) Physical environment matters as well: a cool, dark, and quiet room tends to produce deeper sleep than one that is warm, bright, or noisy. None of these individual habits guarantees a good night's sleep on its own, but together they form a routine that gradually trains the body to expect and enter sleep more easily, much the way a consistent set of cues trains an athlete's body to perform at a certain time each day. (C) Experts commonly recommend going to bed and waking up at the same time every day, even on weekends, because an irregular schedule confuses the body's internal clock and makes it harder to fall asleep on demand.

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

In other words, what looks like a lack of discipline may actually be a biological mismatch. Across many countries, high schools begin classes early in the morning, often before eight o'clock. ( ① ) This schedule assumes that teenagers can simply go to bed earlier to compensate, but biology tells a different story. ( ② ) During adolescence, the body's internal clock shifts later, delaying the release of melatonin until well after ten at night. ( ③ ) As a result, most teenagers are not physiologically ready to fall asleep until much later than younger children or adults are, and 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. ( ④ ) 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. ( ⑤ ) Some school districts that delayed their start times by thirty minutes reported improvements in attendance.