영어 모의고사 (자동 편성)

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

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.

For decades, most vaccines worked by injecting a ①weakened or inactivated version of a pathogen, coaxing the immune system into recognizing an enemy it had never truly fought. mRNA vaccines take a fundamentally ②different route, delivering only a short genetic instruction wrapped in a protective lipid capsule, one that tells the body's own cells how to manufacture a single harmless piece of a virus's outer surface protein. Once those cells display the fragment, the immune system learns to recognize it as ③foreign and builds a defense, without ever having encountered the actual pathogen. Because the vaccine contains no live virus and cannot alter a cell's own DNA, developers can ④redesign the genetic instructions within weeks whenever a pathogen mutates, rather than starting the years-long process required for traditional vaccines. This speed has convinced many researchers that the same platform could eventually be adapted to fight diseases far beyond infectious illness, ⑤excluding certain cancers.

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. During non-REM sleep, especially its deepest stage, the brain waves ①slow down dramatically, the body temperature drops, and tissue repair and growth hormone release reach their peak. This is the period most closely associated with physical ②restoration. REM sleep, by contrast, brings rapid eye movements, near-total muscle paralysis, and brain activity that closely resembles wakefulness. Most vivid dreaming occurs during this stage, and researchers believe it plays a central role in ③ignoring memories and processing emotional experiences. A healthy night typically cycles through both stages four or five times, with non-REM dominating the early hours and REM periods ④lengthening toward morning. Disrupting either stage, through frequent awakenings or alcohol use, can leave a person feeling ⑤unrested even after a full night in bed.

Every cell in the human body follows an internal timer known as the circadian rhythm, a roughly twenty-four-hour cycle that ①governs when we feel alert and when we feel drowsy. This clock is regulated primarily by a tiny cluster of neurons in the brain that responds to light entering through the eyes. When morning sunlight strikes the retina, the cluster signals the body to ②suppress sleep hormones and raise body temperature, preparing us for activity. As evening approaches and light fades, the same mechanism triggers the release of melatonin, a hormone that ③promotes drowsiness. Because this rhythm evolved around the natural cycle of day and night, modern habits such as staying indoors under artificial light or working night shifts can push the internal clock ④out of sync with the external environment. Such misalignment does not simply cause tiredness; it has also been associated with digestive problems and ⑤heightened concentration, suggesting that timing matters as much as total sleep hours.

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 common trigger is what researchers call cognitive hyperarousal, in which _______________. 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. 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.

Many readers assume that once they finish a book, there is no reason to open it again. (A) Some students who reread their favorite novel report that it feels almost like reading a different book, because they now understand the characters' motives more deeply. Teachers therefore encourage students not to rush toward new titles alone, but to occasionally return to a book they already loved, since a second visit often teaches more than the first. (B) Once the ending is already known, a second reading frees the mind to notice smaller things, such as a clever hint the author placed early in the story or a change in a character's tone. (C) Yet teachers who study reading often disagree, arguing that a second reading can reveal details a first reading misses completely. During a first reading, most of a student's attention goes toward simply following the plot, wondering what will happen next.

A smartwatch strapped to a runner's wrist can now do far more than simply count steps; it monitors heart rate variability, running form, and recovery time, then uses that data to suggest a training plan tailored to the individual rather than a generic weekly schedule. (A) Sports scientists note an important caveat, however: a wrist-based sensor cannot fully capture the same physiological detail available in a professional lab. (B) When the device detects signs of overtraining, such as an unusually high resting heart rate several mornings in a row, it may recommend a lighter workout or an extra rest day before fatigue turns into an actual injury. (C) Amateur athletes often credit this kind of guidance with helping them train more consistently without pushing their bodies too hard.

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 )

Treating a wellness app as a substitute for medical expertise, they warn, can be just as risky as ignoring a warning altogether. A growing number of health apps now track steps, sleep, and heart rate throughout the day, quietly building a detailed picture of a user's physical condition without requiring a single visit to a doctor's office. ( ① ) By comparing this stream of data against patterns drawn from millions of other users, the app's algorithm can flag early warning signs, such as an irregular heartbeat, long before the person experiencing it would have noticed anything unusual on their own. ( ② ) For people living far from specialists or unable to afford frequent checkups, this kind of constant monitoring can feel like a genuine safety net. ( ③ ) Doctors caution, however, that these apps are designed to detect patterns, not to diagnose illness. ( ④ ) A worried user should always confirm any alarming reading with a professional rather than trusting an app's suggestion alone. ( ⑤ )