However wealthy we may be, we can never find enough hours in the day to do everything we want. Economics deals with this problem through the concept of opportunity cost, which simply refers to whether someone's time or money could be better spent on something else.

    Every hour of our time has a value. For every hour we work at one job we could quite easily be doing another, or be sleeping or watching a film. Each of these options has a different opportunity cost—namely, what they cost us in missed opportunities.

    Say you intend to watch a football match but the tickets are expensive and it will take you a couple of hours to get to and from the stadium. Why not, you might reason, watch the game from home and use the leftover money and time to have dinner with friends? This—the alternative use of your cash and time—is the opportunity cost.

    For economists, every decision is made by knowledge of what one must forgo—in terms of money and enjoyment—in order to take it up. By knowing precisely what you are receiving and what you are missing out on, you ought to be able to make better-informed, more reasonable decisions. Consider that most famous economic rule of all: there's no such thing as a free lunch. Even if someone offers to take you out to lunch for free, the time you will spend in the restaurant still costs you something in terms of forgone opportunities.

    Some people find the idea of opportunity cost extremely discouraging: imagine spending your entire life calculating whether your time would be better spent elsewhere doing something more profitable or enjoyable. Yet, in a sense it's human nature to do precisely that—we assess the advantages and disadvantages of decisions all the time.

    In the business world, a popular phrase is “value for money.” People want their cash to go as far as possible. However, another is fast obtaining an advantage: “value for time.” The biggest restriction on our resources is the number of hours we can devote to something, so we look to maximize the return we get on our investment of time. By reading this passage you are giving over a bit of your time which could be spent doing other activities, such as sleeping and eating. In return, however, this passage will help you to think like an economist, closely considering the opportunity cost of each of your decisions.

    Both humans and animals have enemies. It is easy for us to know the difference between our friends and our enemies. But can other animals do the same? Elephants can! They can use their sense of vision and smell to tell the difference between people who pose a threat(威胁) and those who do not. In Kenya, researchers find that elephants react differently to clothing worn by men of the Maasai and Kamba ethnic groups. Young Maasai men spear(刺)animals and thus pose a threat to elephants; Kamba men are mainly farmers and are not a danger to elephants.

    In an experiment conducted by animal scientists, elephants were first presented with clean clothing or clothing that had been worn for five days by either a Maasai or a Kamba man. When the elephants noticed the smell of clothing worn by a Maasai man, they moved away from the smell faster and took longer to relax than when they noticed the smells of either clothing worn by Kamba men or clothing that had not been worn at all.

    Clothing color also plays a role. In the same study, when the elephants saw red clothing not worn before, they reacted angrily, as red is typically worn by Maasai men. Rather than running away as they did with the smell, the elephants acted aggressively(攻击地) toward the red clothing.

    The researchers believe that the elephants' emotional(情绪的) reactions are due to their different senses of the smells and the sights. Smelling a potential danger means that a threat is nearby and the best thing to do is run away and hide. Seeing a potential threat without its smell means that risk is low. Therefore, instead of showing fear and running away, the elephants express their anger and become aggressive.

    Many people may not find the idea of visiting Beijing's Forbidden City just to see its cultural relics(遗迹)very exciting. But what if you got to see deer there too? That certainly sounds like a better day out.

    Nine deer were introduced into the Forbidden City, also known as the Palace Museum, on Sept. 26 and would make it their home until February. The beautiful animals are part of an exhibition on deer-related relics, including furniture, clothes and artworks. In ancient China, deer patterns(图案)could be seen on lots of items since lu—deer—were considered to be a lucky animal because the Chinese word shares the pronunciation(发音)of the character that means “official salary(俸禄)”.

    The deer in the Palace Museum are not only to be part of the exhibition, but also to act as ambassadors(大使)to attract visitors. “It's a better way to bring cultural relics closer to the people,”explained Wang Yamin, a deputy director at the Museum, according to ChinaDaily.

    Turning itself into a zoo is the latest effort that the museum has made at introducing academic(学术的)art to ordinary people.

    In 2014, for example, the museum's online store started to offer products such as T-shirts featuring the pattern of an emperor's coat, and earphones looking like the necklaces worn by ancient officials. These products soon gained popularity on social media because they allowed people to wear a piece of history.

    Two years later, the TV series MastersintheForbiddenCity(《我在故宫修文物》)lifted the mysterious veil(面纱)on the experts who work in the museum—people whose job is to repair the relics within it. And while many of us may have imagined these workers to be old and boring, they're actually quite young and interesting. Some are even in their 20s. They lead a peaceful career, although it can sometimes be dull. Workers aren't allowed to wear any make-up or do their nails(指甲)because the chemicals(化学物质)may damage the relics they're working on, for example.

    Little by little, the Palace Museum is shaking off the stereotypes(刻板印象)of being an old-fashioned academic institution. As Shan Jixiang, the museum's director, once said, “Academic research is not alien from the public's interest. We'd like to make visiting the museum a part of people's daily lives. ”

    It looks like the Forbidden City isn't so forbidden after all.

    At first, Michael Surrell didn't see the black smoke or flames shooting from the windows of his neighbors' home. Then they got a call from one of his daughters: "The house next door is on fire!" He went over and saw three women crying madly on their porch (门廊).

    "The baby's in the second floor!" one of the women cried. Though the fire department had been called, Surrell, then 64, bravely ran inside. "The baby" was Tiara Roberts, the woman's granddaughter and a playmate of Surrell's three youngest kids.

Entering the burning house was like "running into a bucket of black paint," Surrell says. The thick smoke caused him to stumble blindly around, burned his eyes, and made it impossible to breathe. The conditions would have been dangerous for anyone, but for Surrell, who has chronic obstructive pulmonary disease(慢性阻塞性肺病), they were life-threatening.

    Taking a deep breath, he moved around in the overwhelming darkness. Because the house had a similar layout to his, he found the stairs and made it to the second floor. Then he heard a soft but clear moan. Still unable to see, Surrell fell to his knees on the hot wood floor. He crawled toward the sound, feeling around for any sign of the girl. Finally, he touched something. A shoe, then an ankle. He pulled Tiara toward him, scooped her into his arms and stood. Turning, he fought through the smoke and ran blindly into the blackness…

    Surrell woke up in the hospital a couple of days later and spent over a week in the hospital. Tiara was released from the hospital after a few days. The fire worsened Surrell's pulmonary condition, and he feels the effects even two years later. As a result, he takes extra medication that helps open his airways. "It's a small price to pay," he says. "I'd do it again in a heartbeat. I wouldn't give it a second thought."

    Before you make friends, you have to decide who you want to be your friends.

    Most people like to have friends who like to do the same kind of things they do.

    The quickest way to make a friend is to smile. When you smile, people think you are friendly and easy to talk to. It may not be easy at first to smile, but remember most people will stay away from a scaled or angry looking.

    One easy way to start a conversation with someone is to say something nice about him. Think about how great you feel when someone says something nice to you. Doesn't it make you want to keep talking to that person?

    Ask your new friends questions about themselves. Who's their favourite singer, where do they live, what do they do after school are all good questions to start a conversation. Make sure you have something to add to the conversation, too. Then someone asks you a question, do have an answer for it. There is nothing that will stop a conversation quicker than a shrug for an answer.

    Kids who show an interest in other kids and who are kind and friendly make good friends. Remember, everyone wants to be around people who like to do similar things and people who are nice to them.

    Lost Huawei

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