영어 모의고사 (자동 편성)

The gig economy, in which people take on short-term or freelance jobs, ①has grown rapidly over the past decade. Digital platforms now connect customers directly with drivers, designers, and writers, ②allowing workers to choose when and how much they work. Businesses, meanwhile, can hire help only when they ③actually need it. For many young people entering the job market, gig work provides valuable flexibility ④that traditional employment rarely allows. However, gig workers often lack benefits such as health insurance, which full-time employees typical ⑤receive.

A short nap taken in the early afternoon, often called a power nap, can noticeably sharpen attention and mood without ①leaving a person groggy afterward. The key lies in timing: naps limited to roughly twenty minutes allow the brain ②to pass through the lightest stages of sleep while avoiding the deeper stages associated with slow-wave activity. If a nap extends much beyond that window, the sleeper risks ③waking during deep sleep, which produces a foggy, disoriented feeling known as sleep inertia that can persist for thirty minutes or more. Laboratory studies ④comparing napping and non-napping groups have repeatedly shown that a brief nap improves reaction time and short-term memory almost as effectively as a full night of extra rest. Interestingly, the benefit appears strongest when the nap occurs several hours after waking, since this is when the body's natural dip in alertness makes rest most ⑤effectively.

After a strenuous workout, muscle fibers experience thousands of ①microscopic tears, and the body immediately begins a repair process that ultimately makes the muscle stronger than it was before. This repair depends heavily on amino acids, the building blocks that protein supplies, which is why sports scientists recommend consuming protein within a couple of hours after training. Waiting too long to eat can ②slow recovery, since a muscle's sensitivity to amino acids gradually declines once that window closes. Many athletes assume that eating an enormous quantity of protein in a single sitting will ③delay this process, but the body can only use a limited amount at once; the rest is simply burned for energy or stored as fat. For this reason, nutritionists generally advise spreading moderate portions of protein ④evenly across several meals throughout the day rather than saving it all for one large post-workout ⑤meal.

Smartphones, tablets, and computer screens all emit a significant amount of blue light, a short-wavelength light that our eyes are especially sensitive to. During the day, exposure to blue light from the sun helps keep us ①drowsy and mentally sharp, which is generally beneficial. At night, however, the same wavelength can interfere with the body's natural preparation for sleep. Specialized cells in the retina detect blue light and send signals to the brain's internal clock, ②suppressing the release of melatonin, the hormone that signals it is time to rest. Studies have found that people who scroll through their phones in bed before sleeping take longer to fall asleep and experience ③lighter, more easily disrupted sleep than those who avoid screens. Some devices now offer a night mode that shifts the display toward ④warmer tones, reducing blue light output in the evening. While this feature may help slightly, sleep researchers generally recommend limiting screen use altogether in the hour before bedtime for the best ⑤results.

Researchers who study teenagers have found a strong link between how well students sleep and how well they perform in school. Students who sleep fewer than seven hours a night tend to score lower on tests of memory and attention than those who sleep eight or nine hours, even when the two groups study for the same number of hours. One explanation is that sleep plays an active role in learning: during certain stages of sleep, the brain replays and strengthens information encountered during the day, _______________. When sleep is cut short, this consolidation process is interrupted before it can finish, so material that seemed well understood the night before often feels unfamiliar the next morning. For this reason, some schools have begun rethinking early start times, reasoning that an extra hour of sleep might do more for test scores than an extra hour of studying ever could.

Every cell in the human body follows an internal timer known as the circadian rhythm, a roughly twenty-four-hour cycle that governs when we feel alert and when we feel drowsy. (A) This clock is regulated primarily by a tiny cluster of neurons in the brain that responds to light entering through the eyes, signaling the body to suppress sleep hormones each morning. (B) As evening approaches and light fades, however, the same mechanism triggers the release of melatonin, a hormone that promotes drowsiness. (C) Because this rhythm evolved around the natural cycle of day and night, modern habits such as artificial light exposure or night shifts can push it out of sync, which has been linked to digestive problems and reduced concentration.

Sleep debt refers to the cumulative gap between the amount of sleep a person needs and the amount they actually get. (A) Unlike a financial debt, however, this deficit cannot simply be repaid with a single long weekend of rest. (B) 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 who has been awake for an entire night. (C) Researchers have found that even modest, chronic sleep restriction gradually impairs reaction time and decision-making, often without the affected person noticing the decline. This is because subjective feelings of tiredness tend to plateau after a few days, even as objective performance keeps deteriorating. Consequently, people frequently underestimate how much sleep debt they are carrying until a demanding task suddenly exposes the accumulated cost.

Treating only one side of this equation, therefore, often leaves the other free to sustain the sleeplessness on its own. 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. ( ① ) 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. ( ② ) 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. ( ③ ) Poor sleep habits, including irregular bedtimes and excessive screen use before bed, can further weaken the body's internal signals for sleep onset. ( ④ ) 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. ( ⑤ )

Its influence, in fact, can persist quietly long after any feeling of alertness has faded. Caffeine is the most widely consumed stimulant in the world, prized for its ability to sharpen focus and fight off fatigue within minutes of consumption. ( ① ) It works by blocking adenosine, a chemical that gradually builds up in the brain throughout the day and makes us feel increasingly sleepy the longer we stay awake. ( ② ) 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. ( ③ ) 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 interfering with the ability to fall asleep at midnight. ( ④ ) Even when people do not consciously notice difficulty falling asleep, caffeine has been shown to reduce the amount of deep, restorative sleep obtained later in the night. ( ⑤ ) For this reason, many sleep specialists advise avoiding caffeine after early afternoon.

In other words, the two stages appear to serve complementary purposes, one restoring the body and the other restoring the mind. Sleep is not a single, uniform state but a cycle that alternates between two very different modes: REM (rapid eye movement) sleep and non-REM sleep. ( ① ) During non-REM sleep, especially its deepest stage, the brain waves slow down dramatically, the body temperature drops, and tissue repair and growth hormone release reach their peak. ( ② ) This is the period most closely associated with physical restoration. ( ③ ) REM sleep, by contrast, brings rapid eye movements, near-total muscle paralysis, and brain activity that closely resembles wakefulness. ( ④ ) Most vivid dreaming occurs during this stage, and researchers believe it plays a central role in consolidating memories and processing emotional experiences. ( ⑤ ) A healthy night typically cycles through both stages four or five times, with non-REM dominating the early hours and REM periods lengthening toward morning. Disrupting either stage, through frequent awakenings or alcohol use, can leave a person feeling unrested even after a full night in bed.