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.

    You eat food and drink water, right? Skipping Rocks Lab is changing how you and your future generations will have water. Have you ever thought you could eat water? Think again, this is actually happening somewhere in the world.

    The group at Skipping Rocks Lab has made a water bottle you can eat. The product is called Ooho. Unlike plastic bottles, Oohos are neither tall nor hard. They look more like bubbles, or small, round, clear balls. They can hold liquid inside. People who drink Oohos can be surprised: the outside bursts in the mouth.

    Rodrigo Garcia Gonzalez is with Skipping Rocks Lab. He explains that the outside, or the membrane, of Ooho is made of seaweed, a plant that grows in the ocean. “It's a membrane made of seaweed that can contain water or any kind of liquid. It's made from an extract (汁) of the brown seaweed.”

    The Ooho membrane is tasteless, and you can eat it. The company says even if you throw away the membrane, it will break down in about four weeks. Gonzalez says the membrane is strong, and good for the environment.

Every year, billions of plastic water bottles are thrown away, polluting land and waterways around the world. The typical water bottle made of plastic can take hundreds of years to degrade.

    Lise Honsinger is also with Skipping Rocks Lab. “Most people just grab a bottle of water, hold it for five minutes, drink it, and throw it away. How can that then exist for 700 years? So, yeah, this is absolutely a solution to that. We are very purist: we don't want to see this packaged in plastic.”

    There are limits to the Ooho. It cannot be refilled. Each bottle is small. And Oohos do not store for more than a few days. The Skipping Rocks Lab is working on those issues. “We're still working on things like extending the shelf life, looking at different options in terms of thickness, if we want to make one that stands up more, or more flexible for marathons where people just want to eat it whole.”

    Right now, Skipping Rocks Lab can make only a few thousand Oohos a day. But it is developing new technology that could increase that number to hundreds of thousands.

    I'm Caty Weaver. Kevin Enochs wrote this story. Anne Ball adapted it for Learning English. Kelly Jean Kelly was the editor.

    Bad news sells. If it bleeds, it leads. No news is good news, and good news is no news. Those are the classic rules for the evening broadcasts and the morning papers. But now that information is being spread and monitored（监控）in different ways, researchers are discovering new rules. By tracking people's e-mails and online posts, scientists have found that good news can spread faster and farther than disasters and sob stories.

    “The 'if it bleeds' rule works for mass media,” says Jonah Berger, a scholar at the University of Pennsylvania. “They want your eyeballs and don't care how you're feeling. But when you share a story with your friends, you care a lot more how they react. You don't want them to think of you as a Debbie Downer.”

    Researchers analyzing word-of-mouth communication-e-mails, Web posts and reviews, face-to-face conversations-found that it tended to be more positive than negative, but that didn't necessarily mean people preferred positive news. Was positive news shared more often simply because people experienced more good things than bad things? To test for that possibility, Dr. Berger looked at how people spread a particular set of news stories: thousands of articles on The New York Times' website. He and a Penn colleague analyzed the “most e-mailed” list for six months. One of his first findings was that articles in the science section were much more likely to make the list than non-science articles. He found that science amazed Times' readers and made them want to share this positive feeling with others.

    Readers also tended to share articles that were exciting or funny, or that inspired negative feelings like anger or anxiety, but not articles that left them merely sad. They needed to be aroused（激发）one way or the other, and they preferred good news to bad. The more positive an article, the more likely it was to be shared, as Dr. Berger explains in his new book, “Contagious: Why Things Catch On.”

    The insects are important to farmers. When a honeybee lands on a flower in plant, pollen (花粉) sticks to its legs. When the bee lands on another flower, some of the pollen falls off and fertilizes the second plant.

    The act of spreading pollen is responsible for many fruits, vegetables, nuts and other crops. Yet about 30 percent of honeybees in the United States and other areas have died in recent years.

    Mike Leggett is a researcher at the University of Maryland. He wants to learn why so many bees are dying. “The number of colonies (蜂群) that die every winter has been one in three. So on average 30 percent of the colonies have died every winter over the last six winters. And that's a huge number.” His research team examined the pollen that honeybees carried to their homes. They found that the pollen contained high levels of 35 different pesticides (杀虫剂), which are chemicals used to protect plants. “Pesticides are used, and have been used, pretty widely, for centuries, to protect plants from diseases,” says Mr Leggett.

    Keith Oh linger, a farmer and beekeeper in Maryland, has watched many of his bees die every winter. Mr Ohlinger thinks widespread bee death is caused by several things happening at once. But he does not feel sure that pesticides are a part of the problem, “I felt it was the result of a lot of little things. I didn't feel that there was probably one smoking gun. But there's a division (分歧) there, some people feel that it is just one thing.”

    Honeybees are important to agriculture. This makes the search for an answer to their death very important for Mr Leggett's team. As he knows, one in every three bites of food we eat is somehow pollinated by honeybees.

    You're sitting on the sofa, and there's your dog, right at your feet. You stand up? He stands up. But then you head to the bathroom, and guess who comes with? Why, your dog, of course. But why? Why does your dog follow you like a shadow, no matter where you go?

    Ever get the feeling you're being followed? As for why your companion follows you everywhere you go, read on!

    "When dogs follow their owners, there can be several scientific explanations, depending on the dog and the individual situation," according to Mary Burch, Ph.D., an animal behaviorist(行为学家).

    These explanations include:

    Positive reinforcement(正面强化): When your dog follows you, good things happen. Think dog food, a hot bath and taking a walk around the neighborhood. Your dog's no dummy. And one of his many talents is learning from experience, that is "reinforcement."

    Natural instinct(本能) to be part of a pack: In fact, a study out of Princeton University that was published in the journal, Science Advances, shows that your dog's drive (驱动力)to follow you around (as well as watch you attentively and seek physical contact (身体接触) from you) lies in his genes(基因).

    Feel good chemicals(化学物质): Your presence causes your dog's brain to release "feel good" chemicals, Dr. Primm explains, citing this study. Considering how much we as humans enjoy those feel-good chemicals, it's no surprise your dog likes them too—and will follow you around to get some!

    Sense of responsibility : As you move about your home, your dog might feel that you are patrolling your territory (巡视领地) and take on the duty to assist you.

    Here are some events in the following months. Have a look and pick out your favorite.

    AVCS Informational Tour

    Aliso Viejo Christian School, a highly rated private school, which serves children in grades, invites potential families to its annual AVCS informational tour. Come and see its facility, meet its staff, check out its curriculum and amazing programs. The tour would love to share the school with you and answer any questions.

    Location: AVCS Campus

    German Immigrants Exhibition

    German immigrants played a huge role in shaping Indianapolis through the 19th century. They brought educational reform, political activity and greenhouse farming. In addition to produce, these immigrants also kept their communities full of flowers and trees, know about this part of history in October.

    Location: Indiana Historical Society

    Whale Watching

    Gray whales migrate (迁徙) annually along the west coast of North America. They can be seen from the Orange County coast from December through early April. Summer and fall bring the giant blue whales. They can be seen from June through September. Since the gray whales migrate just a few miles off the coast, simple sail from Newport Beach enables you to see these spectacular creatures in their natural habitat.

    Location: Newport Beach

    Sunday Brunch(早午餐)

    Sunday brunch is a wonderful way to enjoy your weekend. At View Restaurant, Sunday brunch is always accompanied by champagne, spectacular views and unique atmosphere. The menu includes traditional breakfast foods and lunch favorites like barbeque and fresh fish selections. You can also choose to view sporting events in the restaurant. With enough variety to satisfy every appetite from kids to adults, this is one Sunday brunch you'll keep coming back to!

    Location: View Restaurant