Grammar is the system of a language. People sometimes describe grammar as the “rules” of a language; but in fact no language has rules. If we use the word “rules”, we suggest that somebody created the rules first and then spoke the language, like a new game. But languages did not start like that. Languages started by people making sounds which evolved (逐渐发展成) into words, phrases and sentences. No commonly-spoken language is fixed. All languages change over time. What we call “grammar” is simply a reflection (反映) of a language at a particular time.

    Do we need to study grammar to learn a language? The short answer is “no”. Very many people in the world speak their own, native language without having studied its grammar. Children start to speak before they even know the word“grammar”. But if you are serious about learning a foreign language, the long answer is “yes, grammar can help you to learn a language more quickly and more efficiently.” It's important to think of grammar as something that can help you, like a friend. When you understand the grammar (or system) of a language, you can understand many things yourself, without having to ask a teacher or look in a book.

So think of grammar as something good, something positive, something that you can use to find your way—like a signpost(路标) or a map.

    Except invented languages like Esperanto（世界语）. And if Esperanto were widely spoken, its rules would soon be very different.

    The most widespread fallacy (谬论)of all is that colds ire caused by cold. They are actually caused by viruses passing on from person to person. You catch a cold by coining into contact, directly or indirectly, with someone who already has one. If cold causes colds, it would be reasonable to expect the Eskimos to suffer from them forever. But they do not. And in the isolated Arctic Regions explorers have reported being free from colds until coming into contact again with infected people from the outside world by way of packages and mail dropped from airplanes.

    During the First World War soldiers who spent long periods in the trenches(战壕), cold and wet, showed no increased tendency to catch colds.

    In the Second World War prisoners at the Auschwitz concentration camp，naked and starving, were astonished to find that they seldom had colds. At the Common Cold Research Unit in England, volunteers took part in experiments in which they gave themselves to the discomforts of being cold and wet for long stretches of time. After taking hot baths, they put on bathing suits, allowed themselves to be with cold water, and then stood about dripping wet in drafty rooms. Some wore wet socks all day while others exercised in the rain until close to exhaustion. Not one of the volunteers came down with a cold unless a cold virus was actually dropped in his nose.

    If then, cold and wet have nothing to do with catching colds, why are they more frequent in the winter. Despite the most pains-taking research, no one has yet found the answer. One explanation offered by scientists is that people tend to stay together indoors more in cold weather than at other times, and this makes it easier for cold viruses to be passed on.

B

    Asking for salary history provides an easy way to sort applicants into an employer's desired price range and helps the employer calculate the lowest offer that will still attract a candidate. But an increasing number of U.S. states and cities agree there ought to be a law against it. Massachusetts, Philadelphia, New York City and Puerto Rico have banned salary history questions on applications and in interviews.

    Why? Because when it comes to a candidate's suitability for a job, salary history is a subjective (主观的) and often misleading indicator — and it may most affect ＂the people who have already been illegally treated,＂ says Katie Donovan, a salary negotiation coach and one of the authors of the Massachusetts law.

    Candidates who start their careers underpaid because of the gender (性别) or race wage gap, a bad economy or a cheap boss finds that this lowball (虚报低价) figure continues to weigh them down throughout their career. At the same time, senior victims of layoffs have difficulty being hired because employers assume they're not interested in senior victims.

    In an interview, you can avoid talking about salary history questions by turning the discussion to what you're looking to make.

    Donovan recommends a method similar to what you're already doing: Enter $0.00, or some other number that is clearly intended not to cheat, but to oppose.

    Of course, there's always a risk doing so because it will cost you opportunities. But Ronda Wakefield, owner of NW MT HR Solutions, says that when she receives an application with an obviously false salary history, she'll still follow up if the candidate interests her. ＂I personally don't want to miss out on a great candidate because they didn't want to answer the question directly,＂ she says.

    Metro Pocket Guide

    Metrorail(地铁)

    Each passenger needs a farecard to enter and go out. Up to two children under age five may travel free with a paying customer.

    Farecard machines are in every station. Bring small bills because there are no change machines in the stations and farecard machines only provide up to $5 in change.

    Get one day of unlimited Metrorail rides with a One Day Pass. Buy it from a farecard machine in Metro stations. Use it after 9：30 am until closing on weekdays, and all day on weekends and holidays.

    Hours of service

Open: 5 am Mon.—Fri.         7 am Sat.—Sun.

Close: midnight Sun.—Thur.    3 am Fri.—Sat. nights

    Last train times vary. To avoid missing the last train, please check the last train times posted in stations.

    Metrobus

    When paying with exact change, the fare is $1.35. When paying with a SmarTrip^® card, the fare is $1.25.

    Fares for senior/disabled customers

    Senior citizens 65 and older and disabled customers may ride for half the regular fare. On Metrorail and Metrobus, use a senior/disabled farecard or SmarTrip^® card. For more information about buying senior/disabled farecards, SmarTrip^® cards and passes, please visit MetroOpensDoors.com or call 202­637­7000 and 202­637­8000.

    Senior citizens and disabled customers can get free guide on how to use proper Metrobus and Metrorail services by calling 202­962­1100.

Travel tips(提示)

    •Avoid riding during weekday rush periods—before 9：30 am and between 4 and 6 pm.

    If you lose something on a bus or train or in a station, please call Lost & Found at 202­962­1195.

    Lights out, phones on. Many teenagers reach for their smartphones or tablets at bedtime, but it may be a good idea to switch off before you hit the pillow.

    According to a study by researchers at Murdoch and Griffith Universities in Australia, using mobile devices late at night could harm teenagers' sleep and lead to an increased risk of mental health problems.

    The study was carried out on more than 1,000 Australian high school students aged between 13 and 16. It lasted four years as student participants moved from Year 8 to Year 11.

    During the study, students were asked what time of the night they received or sent text messages and phone calls, and how well they slept.

    The results are impressive. When the study started in Year 8, more than 85 percent of the students had a mobile pone and around one-third of these students never used phones after lights out. In contrast, 93 percent of Year 11 students had a mobile phone and only 22 percent of then had no late night mobile use when the study concluded four years later.

    As the levels of mobile phone use increased, there was a growth in poor sleep behavior among the students. Meanwhile, mental health problems also increased. Students in Year 8 who were more likely to use phones at night were found to have higher levels of depression (抑郁) and lower self-esteem (自尊心) one year later.

    Lynette Vernon, lead author of the study, explained that phones affect our sleep patterns because of the unnatural blue light they produce. This light could affect the level of hormones (荷尔蒙) in the body, disrupting (打乱) its balance.

     “The more you sit in bed and watch TV, play with your tablet, and play with your phone at three o'clock in the morning, the more these things affect the slow waves of your sleep pattern and give your poor quality sleep,” Mark Levi, a Sydney-based sleep doctor said.

    Based on the findings, the researchers suggested parents should focus on guiding their children's use of mobile devices.

    According to Vernon, the solution is not simply to ban teenagers from using their devices, but teach them better ways of using them

     “Back when they're aged 7 to 10, you have to be a role model. If you put your phone away at night and it doesn't go into your bedroom, it becomes normalizedin the household and you have a much easier job,” he told The Guardian.

    A family in Florida had a happy Christmas this year thanks to two local police officers, who answered a 911 call only to discover there was no emergency at all.

    When they arrived at the house of a single mother with two children, the officers discovered the younger child, about two years old, was playing with the phone. There were no signs of Christmas or holiday cheer in the house. "They weren't smiling. It seemed like they weren't happy at all. They were missing something," Officer Paramore said. "The mother mentioned that they weren't going to have a Christmas that year. It was pretty obvious that the family was struggling," he said. "So we told each other that something had to be done."

    Paramore and his partner, Barry Ward, left the house with a plan. The next day, they went to a supermarket and bought a tree, lights and some ornaments (装饰物) with their own money. Then they returned to the apartment to deliver some holiday cheer. "They hugged the tree," Paramore said. "I was glad to see that this family was going to have something to sit around and use." The police department posted the video on YouTube, hoping to share the happy news and inspire others.

    The department has received tons of donations and phone calls from people around the country asking how they can help the family. "We are covered," said Stephanie Slater, public information officer for the Boynton Beach Police Department. "We're asking people to do good in their communities on behalf of our officers. We appreciate it very much that people are talking about this after watching the news on TV because they need to see and need to be reminded that police officers are good guys," she said. "They are human beings who have a kind heart and they do things that go unnoticed like this every day."