The term “to extend an olive（橄榄） branch” means to make an offer of peace or reconciliation(和好). This term has Biblical（圣经的）origins, coming from the section of the Old Testament that deals with the flood; the sign that the flood is over is an olive branch brought back to the ark(方舟) by a dove. Olive branches were also symbols of peace in Ancient Greece and Rome, and they continue to be used in various works of art that are meant to suggest peace.

    Some people have suggested that the olive was a very deliberate and well-considered choice as a metaphor(比喻）for peace, because olive trees famously take years to mature. War is typically very hard on the trees because people cannot take the time to nurture them and plant new ones. Therefore, the offer of an olive branch would suggest that someone is tired of war, whether it is an actual war or a falling out between friends.

    In Ancient Greek and Roman times, people would offer actual olive branches. In Rome, for example, defeated armies traditionally carried olive branches to indicate that they were giving in, and the Greeks used them into weddings and other ceremonies. In the modern era, the branch is usually metaphorical, rather than actual, not least because the plants can be a bit difficult to obtain.

    Many people agree that peace negotiations at all levels of society are a good idea. Between nations, obviously, it is important to extend an olive branch to ensure mutual safety and to help the world run more smoothly. This act can also be important on a personal level, as resolving conflict and learning to get along with others is viewed as an important life skill in many cultures.

    At some point in their lives, many people will be advised to extend an olive branch to settle a dispute or resolve an issue. Some people believe that it takes an immense amount of courage to take this action, as it often comes with an admission of wrongdoing and regret.

    Zhang Kui first learned he could perfectly mimic(模仿)the sounds of animals when he was a child. The 29-year-old, who grew up in a poor family in Qiyang, Human province, today is a full-time performer of kouji.

    Zhang was 15 when his father died in 2003. He dropped out of school and joined his uncle's theater. Zhang bought CDs to study how to mimic the sounds of musical instruments and animals. He performed shortly afterward at a small theatre. “Although I wasn't that skilled, I got a lot applause(掌声). It was my first time on the stage. And then more and more audience came to watch my performances.” he said.

    He moved to Guilin in 2004, where he found work as a waiter at a karaoke bar. In 2005, Zhang went to Guangdong province and performed outside supermarkets to sell shampoo. “They paid me less, so I had to perform at bars at night.” said Zhang. He also worked as a condtruction worker. In 2007, he went to Beijing to learn from Niu Yuliang, a Beijing Kouji master. He worked as a gatekeeper to pay his way. He went to Niu on weekends and during the holidays to learn.

    Zhang's skills improved and he has since performed on more than 20 television programs. In September 2013, he was invited to Switzerland, in 2004, he performed in Africa, Europe and North America.

    Last year, he made a short film about the art and said it was the first film on the subject. The film will be on this year, and he said he hoped to draw more attention to the art. He also plans to give lectures on this traditional art at universities.

    The legal age for drinking alcohol（酒精饮料） in the US is twenty-one. Underage drinking is not only a crime but also a common part of college social life. This week in our Foreign Student Series, we look at alcohol policies at American colleges and universities.

    The United States has more than 17 million students in higher education. Each year, 1,700 of them aged 18 to 24 die from alcohol-related road crashes and other injuries. 600,000 more are injured because of alcohol. And almost 700,000 are attacked by another student who has been drinking.

    Now, many schools have begun to strengthen（加强）their rules and college officials are trying to prevent too much drinking. Some researchers have found that students who think heavy drinking is normal often think that other students really drink much.

    At the University of Oklahoma, new policies came into effect after a nineteen-year-old student died from drinking too much at a party. Now alcohol is banned（禁止） from all university housing. Student organizations can serve alcohol at events but only on Friday and Saturday nights. And they must provide for transportation to and from off-campus parties. Other new requirements include an alcohol educational program that first-year students take online.

    The policies govern behavior on campus and off. With the first violation（违规）, students pay

75 dollars and their parents are told. They must also take an alcohol education class. They have to pay double if the behavior happens again. Those who violate a third time will have to be driven home for at least one term. The president of Oklahoma says the aim is not just to punish but to change the behavior and the culture at the university.

    Escaping predators (食肉动物), digestion and other animal activities—including those of humans—require oxygen. But that essential ingredient is no longer so easy for marine life to obtain, several new studies reveal.

    In the past decade ocean oxygen levels have taken a dive—an alarming trend that is linked to climate change, says Andreas Oschlies, an oceanographer at the Helmholtz Center for Ocean Research in Germany, whose team tracks ocean oxygen levels worldwide. "We were surprised by the intensity of the changes we saw, how rapidly oxygen is going down in the ocean and how large the effects on marine ecosystems are," he says. It is no surprise to scientists that warming oceans are losing oxygen, but the scale of the drop calls for urgent attention. Oxygen levels in some tropical (热带的) regions have dropped by an astonishing 40 percent in the last 50 years, some recent studies reveal. Levels have dropped less significantly elsewhere, with an average loss of 2 percent globally.

    A warming ocean loses oxygen for two reasons: First, the warmer a liquid becomes, the less gas it can hold. That is why carbonated drinks go flat faster when left in the sun. Second, as polar sea ice melts, it forms a layer of water above colder, more salty sea waters. This process creates a sort of lid that can keep currents from mixing surface water down to deeper depths. And because all oxygen enters the surface, less mixing means less of it at depth.

    Ocean animals large and small, however, respond to even slight changes in oxygen by seeking refuge in higher oxygen zones or by adjusting behavior, Oschlies and others in his field have found. These adjustments can expose animals to new predators or force them into food-scarce regions. Climate change already poses serious problems for marine life, such as ocean acidification, but deoxygenation is the most pressing issue facing sea animals today, Oschlies says. After all, he says, "they all have to breathe."

    Aside from food web problems, animals face various other physiological challenges as their bodies adjust to lower oxygen levels. Chinese shrimp (虾) move their tails less vigorously to preserve energy in lower oxygen environments. Some creatures, such as jellyfishes, are more tolerant of low oxygen than others are. But all animals will feel the impact of deoxygenation because they all have evolved their oxygen capacity for a reason, says Oschlies. "Any drop in oxygen is going to damage survivability and performance," he says.

    Sometimes people add to what they say even when they don't talk. Gestures are the "silent language" of every culture. We point a finger or move another part of the body to show what we want to say. It is important to know the body language of every country or we may be misunderstood.

    In the USA, people greet each other with a handshake in a formal introduction. The handshake must be firm. If the handshake is weak, it is a sign of weakness or unfriendliness. Friends may place a hand on the other's arm or shoulder. Some people, usually women, greet a friend with a hug.

    Space is important to Americans. When two people talk to each other, they usually stand about two and a half feet away and at an angle (角度), so they are not facing each other directly. Americans get uncomfortable when a person stands too close. They will move back to have their space. If Americans touch another person by accident, they say, "Pardon me" or "Excuse me". Americans like to look at the other person in the eyes when they are talking. If you don't do so, it means you are bored, hiding something, or are not interested. But when you stare at someone, it is not polite.

    For Americans, thumbs-up means yes, very good, or well done. Thumbs-down means the opposite. To call a waiter, raise one hand to head level or above. To show you want the check, make a movement with your hands as if you are signing a piece of paper. It is all right to point at things but not at people with the hand and index finger (食指). Americans shake their index finger at children when they scold them and pat them on the head when they admire them.

    Learning a culture's body language is sometimes confusing. If you don't know what to do, the safest thing to do is to smile.

Earthquakes are common natural disasters. No matter where you are, knowing how to protect yourself and your family during an earthquake is necessary.

Some experts believe that when you feel the ground is shaking, drop down, take cover under a desk and hold on. Most earthquake injuries are the result of being hit by something falling on you. You should stay indoors until the shaking stops. If you are outdoors, don't stay near buildings, trees or power lines. Many people think that in case of an earthquake, they should "get under something" like a doorway or desk, in order to avoid being hurt by falling objects. Rescue experts now say this is the wrong thing to do. For example, in the 1985 Mexico City earthquake, they found hundreds of children in schools, crushed by their desks. However, they could have survived by lying in the aisle (通道，走道) next to their desks.

So find a nice piece of furniture, a chair, a sofa, and lie down, or curl up next to it. A falling roof may compact (压实) the furniture, but will still leave a space for you to survive next to it. This also holds true if you are in a hotel room, especially at night. Get off the bed, and lie down next to it.

In San Francisco's 1989 earthquake, the upper freeway fell on the lower one. People who drove along were crushed in their cars. But they had time to get out and lie down next to their cars. Yes, their cars were crushed, but there was space from top to bottom next to the vehicles for people to survive and wait a rescue.

Doorways and stairways are very unsafe. Stay away from those.

What can we do to keep ourselves safe? Staying calm is the first and most important rule when facing accidents.