영어 모의고사 (자동 편성)

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 shifts later, ①making it difficult for teenagers to fall asleep before eleven at night. Yet school start times rarely adjust to this shift, ②forcing students to wake before their bodies are ready. The consequences extend well beyond simple tiredness. Chronic sleep loss during adolescence has been linked to impaired concentration, weakened memory, and a higher risk of anxiety and depression. It can also disrupt the hormones ③that regulating appetite, contributing to unhealthy weight gain over time. Some school districts have experimented with ④delaying start times by even thirty minutes, and early results suggest that students who gain that extra rest show improved grades, better mood, and fewer tardy arrivals. Despite this evidence, changing entrenched school schedules ⑤remains a slow and contentious process.

Travelers who cross several time zones in a single flight often arrive ①feeling exhausted, foggy, and strangely out of sync with the local clock. The discomfort arises because the body's internal clock, ②which governs sleep, hunger, and alertness, continues to run on the schedule of the departure city even after landing. Realigning this internal clock to a new time zone is not instantaneous; researchers estimate that the body typically needs about one day ③to adjust for every time zone crossed. Flying eastward tends to produce more severe symptoms than flying westward, because advancing the internal clock forward ④are generally harder for the body than delaying it. Exposure to natural light at the right moments after arrival can help speed up the adjustment, since light is the strongest external cue the internal clock ⑤uses to reset itself.

Beyond restoring lost function, engineers are now exploring implants and prosthetics designed to give healthy people abilities beyond ordinary human limits, from night vision to reaction times faster than any athlete could achieve through training alone. Supporters frame this as simply the next step in a long history of human enhancement, ①no different in principle from eyeglasses or vaccines, only more direct. Critics counter that earlier enhancements were broadly available to anyone regardless of wealth, while cutting-edge neural and physical implants are likely to remain ②expensive for decades, potentially splitting society into those who can afford enhancement and those who cannot. If such a divide hardens, competitive advantages in school, sports, and the workplace could come to depend ③less on effort than on access to capital. What began as a medical tool for restoring what was lost, in other words, may end up ④preserving the baseline of what counts as an ordinary human being, keeping the definition of "normal" ⑤unchanged for future generations.

Parents and coaches sometimes worry that heavy resistance training might damage the growth plates in a young athlete's bones, cartilage regions near the ends of long bones that are ①responsible for lengthening as a child develops. This concern kept strength training out of many youth programs for decades. However, extensive research over the past twenty years has found ②little evidence that properly supervised resistance training harms growth plates in healthy children. The actual risk arises not from lifting weights itself but from ③poor technique, excessive load, and inadequate supervision. Major pediatric and sports medicine organizations now generally agree that structured strength programs, when taught with correct form and appropriate weight, can safely ④improve bone density, coordination, and injury resistance in young athletes. The key variable, in other words, is not whether children lift weights but how carefully that training is ⑤ignored.

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. By comparing this stream of data against patterns drawn from millions of other users, the app's algorithm can ①flag early warning signs, such as an irregular heartbeat, long before the person experiencing it would have noticed anything unusual on their own. For people living far from specialists or unable to afford frequent checkups, this kind of constant monitoring can feel like a genuine ②safety net. Doctors caution, however, that these apps are designed to ③diagnose illness, not merely to detect patterns, and that a worried user should always confirm any alarming reading with a professional rather than trusting an app's suggestion alone. Treating a wellness app as a ④substitute for medical expertise, they warn, can be just as risky as ⑤ignoring a warning altogether.

A cluster of neurons smaller than a pea can now spontaneously organize itself into layered structures that mimic, in miniature, the architecture of a developing human brain. Grown from stem cells coaxed to follow the same developmental cues that guide an embryo, these brain organoids have begun firing electrical signals in patterns that faintly resemble the activity recorded in an infant's brain. For researchers studying disorders such as autism or schizophrenia, this offers something long unavailable: a living model of human brain development that can be observed and manipulated directly, without ever touching an actual patient. Because organoids lack sensory organs, a body, or any connection to the outside world, most neuroscientists argue that the structures cannot generate anything resembling subjective experience, however brain-like their electrical activity may appear. _______________.

VO2 max, defined as the maximum volume of oxygen a person's body can consume and use during intense exercise, is widely regarded as one of the best single indicators of cardiorespiratory fitness. (A) Elite endurance athletes typically post VO2 max values far higher than those of untrained individuals, reflecting hearts that pump larger volumes of blood and muscles that extract oxygen with remarkable efficiency. (B) While genetics accounts for a substantial portion of an individual's potential VO2 max, consistent aerobic training can still raise the measurement considerably over months of dedicated effort. (C) It is worth noting, however, that a high VO2 max does not guarantee success in competition, since other factors such as pacing strategy and mental resilience also play a decisive role.

Recovering from a serious sports injury involves far more than simply waiting for torn tissue to heal; it requires a carefully structured program that gradually reintroduces stress to the affected area. (A) Progressing too quickly at this stage is a common mistake, since tissue that appears healed on the surface may still be structurally fragile beneath it. (B) Skipping the final stage of sport-specific drills, even when an athlete feels fully recovered, dramatically increases the risk of re-injury, because general strength does not automatically translate into the coordination a sport demands. (C) Immediately after an injury, rest and gentle range-of-motion exercises give way to light resistance training as pain subsides, slowly rebuilding strength in muscles weakened by disuse.

In response, some platforms have begun inserting occasional wildcard suggestions that are deliberately unrelated to past viewing habits. After a viewer finishes an episode, a streaming service rarely leaves the choice of what to watch next entirely up to chance. ( ① ) Instead, a recommendation algorithm compares that viewer's habits with patterns drawn from millions of other users who watched similar content, then ranks thousands of titles in order of predicted interest. ( ② ) 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. ( ③ ) The system is not without drawbacks, however. Because the algorithm favors titles similar to what a viewer already enjoys, it can quietly narrow someone's exposure to unfamiliar genres, directors, or cultures, creating a comfortable but repetitive bubble. ( ④ ) These wildcard picks are meant to counteract this narrowing effect and keep recommendations from becoming too predictable. ( 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.