For many of us, a little time with our smartphones or iPads before sleep is the highlight of the night. But would you still think it is relaxing if you knew that it damages or destroys your sleep? Scientists say that's exactly what it does. In ancient times, when there were no lamps, telephones or smartphones, the sun was the main source of light. When the sun went down, our brains took that as a signal to start producing melatonin , a chemical that helps us sleep. However, a healthy amount of melatonin can only be produced in complete darkness.Any light in your bedroom--even the one on the alarm clock or the charging indicator on your cellphone--could disturb the process, not to mention something as bright as smartphone and iPad screens. We tend to hold these much closer than a television or laptop, which allows them to shoot far more light straight into our eyes. "This is particularly worrisome in populations such as young adults and adolescents, who already tend to be _ ," said researcher Brittany Wood at Rensselaer Polytechnic Institute."Lack of sleep among teens is leading to depression, selfharm, low concentration and poor performance at school," she added. While all lights are the enemy of sleep, not all colors of light have the same effect. Our eyes are particularly sensitive to blue light, which is common during the day. Most of the light coming from electronic screens is blue light and it fools our brain into thinking it's still daytime. By contrast, orange or red light has less influence on melatonin production, because our brains recognize it as a signal that the day is ending, according to The Telegraph. Asking yourself to keep your hands off your smartphone before bedtime might seem unreasonable, but you should at least remember to dim the screen or hold it farther away from your eyes. You could also wear a pair of orange sunglasses that take away the harmful blue light. In the writer's opinion, which is a correct suggestion? A) You should go to bed when the sun goes down. B) You should use an orange or red light electronic screen. C) You should wear a pair of blue sunglasses when sleeping. D) You should avoid blue light as possible as you can before bedtime.
D
Very old people do raise moral problems for almost everyone who comes into touch with them. Their values - this can't be repeated too often - are not necessarily our values. Physical comfort, cleanness and order are not necessarily the most important for them. The social services from time to time find themselves faced with a flat with going bad food covered with dust on the table, and an old person lying alone on bed, taking no notice of anything. Is it doing harm to personal freedom to insist that they go to live with some of their s so that they might be taken better care of? Some social workers are the ones who clean up the dust, thinking we are in danger of carrying this idea of personal freedom to the point where serious risks are being taken with the health and safety of the old. Indeed, the old can be easily hurt or harmed. The body is like a car; it needs more care as it gets older. You can carry this comparison right through to the provision of spare parts. Never forget that such operations are painful experiences, however good the results. At what point should you stop treating the old body? Is it right to try to push off death by using drugs to excite the forgetful old mind and to activate the old body, knowing that there is little hope? You cannot ask doctors or scientists to decide, because so long as they can see the technical opportunities, they will feel sure to have a try on the belief that while there's life, there's hope. When you talk to the old people, however, you are forced to the conclusion that whether age is happy or unpleasant depends less on money or on health than _ does on your ability to have fun. The author thinks that _ . A) the opinion that we should try every means possible to save old people is doubtful B) medical decisions for the old people should be left to the doctors C) old people can enjoy a happy life only if they are very rich D) it is always right to treat old people and push off death
A
Q: Look closely at ,your hands-are they clean? It doesn't matter how many times you was your hands. They're still crowded with microbes, which are also called "germs" or "bacteria". Microbes are everywhere. But don't worry-most microbes don't harm you. and many actually help you stay alive. Now, scientists say the microbes that live on our hands could be used in a surprising way: fighting crime. When police visit the scene of a crime, they often look for fingerprints to try to identifythe criminal. But according to a recent study, investigators could even use microbes to help break a criminal case. Every person has his or her own set of microbes that live on their hands, according to scientists at,the University of:Colorado. That means the mix of different kinds of microbes on everybody's hand is unique-much like one's fingerprint. The scientists wanted to know whether this microbe mix could be used as a new kind of fingerprint-especially in a crime scene where fingerprints might be hard to find. And policemen use forensics such as studying fingerprints to identify the criminal. "Microbe fingerprints are harder to hide," said Noah Fierer, one of the scientists. "You can't sterilize(......) a surface just by wiping it off. " His team compared the bacteria on the hands of 273 people with the bacteria found on each person's computer keyboard. For the study, the keyboards had been used only by the people who were being tested. The study showed that the mix of microbes from each per- son's hands matched the mix of microbes on that person's keyboard. The scientists were easily able to tell the 273 people apart-just by looking at their keyboards. But there are a lot more than 273 criminals. Other scientists wonder whetherthe microbe fingerprint can really be that useful. Fierer agrees that scientists have a lot more work to do before the microbe fingerprint will be a useful tool. What did Fierer's team find through the study? A) They found the criminal among the 237 people. B) They could tell who had used which computer. C) Computer keyboards couldn't keep people's microbe fingerprints. D) People's characters could be identified by the keyboards they used.
A: B
(Question)
First,you ought to know that I'm "only" fourteen.My mother points this out often.I can make my own decisions when I'm old enough to vote,she says.Second,I should tell you that she's right -- I'm not always responsible.I sometimes take the prize for grade-A dork .Take last weekend for instance.I was staying at Dad's,and I decided it was time I learned to drive.It was Sunday morning,7 A.M.,and I hadn't slept well.I'd been up thinking about an argument,which I'll tell you about in a minute.Well,nobody was up yet in the neighborhood,so I thought it couldn't hurt to back the car out of the garage and drive around the block.But Dad has a clutch car.The "R" on the shift handle was up on the left side,right next to first gear .I guess you can guess the rest. Dad's always been understanding.He didn't say,"Okay,little Miss Know-It-All,you can just spend the rest of the year paying this off," which is what Mom would have said.Instead,Dad worried about what might have happened to me.And that made me feel more guilty than anything.I think he'd be a better number-one caregiver,but I can't say things like that to Mom.To her,I have to say,"But Mom,Dad's place is closer to school.I could ride my bike," to which she replies,"Amy Lynn,you don't own a bike.Remember? You left it in the yard,and it was stolen.And you haven't got the patience to earn the money to replace it." The main conflict between the writer and her mother is about whether she _ . A) can make her own decisions B) should live with her mom or her dad C) should be allowed to drive D) should pay for things she loses or breaks
(Answer)
A