It's true that quite a few most respected scientific authorities have confirmed that the world is becoming hotter and hotter. There^'s also strong evidence that humans are contributing to the warming. Countless recent reports have proved the same thing. For instance, a 2010 summary about the climate science by the Royal Society noted that: The global warming over the last half - century has been caused mainly by human activity.”

    You may not believe that humans could change the planet's climate, but the basic science is well understood. Each year, billions of tons of greenhouse gases are released into the atmosphere because of human activity. As has been known for years, these gases hold heat that would otherwise escape to space, wrapping the planet in an invisible blanket.

    Of course, the earth's climate has always been changing due to “natural” factors such as volcanic eruption or changes in solar, or cycles concerning the Earth's going around the sun. According to the scientific research, however, the warming observed by now matches the pattern of warming we would expect from a build - up of greenhouse gas in the atmosphere - not the warming we would expect from other possible causes.

    Even if scientists did discover another reasonable explanation for the warming recorded so far, that would give birth to a difficult question. As Robert Henson puts it: “If some newly discovered factor is to blame for the climate change, then why aren't carbon dioxide and the other greenhouse gases producing the warming that basic physics tells us they should be?”

    The only way to prove with 100% certainty that humans are responsible for global warming would be to run an experiment with two identical Earths-one with human influence and one without. That obviously isn't possible, and so most scientists are careful not to state human influence as an absolute certainty.

阅读下列短文，从每题所给的四个选项 （A 、B 、C  和 D ）中，选出最佳选项。

    In an ideal world, people would not test medicines on animals. Such experiments are stressful and sometimes painful for animals, and expensive and time-consuming for people. Yet animal experimentation is still needed to help bridge vast gaps in medical knowledge. That is why there are some 50 to 100 million animals used in research around the world each year.

    Europe, on the whole, has the world's most restrictive (严格的) laws on animal experiments. Even so，its scientists use some 12 million animals a year, most of them mice and rats, for medical research. Official statistics show that just 1.1 million animals are used in research in America each year. But that is misleading. The American authorities do not think mice and rats are worth counting and, as these are the most common laboratory animals, the true figure is much higher. Japan and China have even less comprehensive (全面的) data than America.

    Now Europe is reforming the rules governing animal experiments by restricting the number of animals used in labs. Alternatives to animal testing，such as using human tissue or computer models, are now strongly recommended. In addition, sharing all research results freely should help to reduce the number of animals for scientific use. At present, scientists often share only the results of successful experiments. If their findings do not fit the hypothesis (假设) being tested, the work never sees the light of day. This practice means wasting time, money, and animals' lives in endlessly repeating the failed experiments.

    Animal experimentation has taught humanity a great deal and saved countless lives. It needs to continue，even if that means animals sometimes suffer. Europe's new measures should eventually both reduce the number of animals used in experiments and improve the way in which scientific research is conducted.

    Many animals recognize their food because they see it. So do humans. When you see an apple or a piece of chocolate you know that these are things you can eat. You can also use other senses when you choose your food. You may like it because if smells good or because it tastes good. You may dislike sonic types of food because they do not look, smell or taste very nice. Different animals use different senses to find and choose their food. A few animals depend on only one or their senses, while most animals use more than one sense.

    Although there are many different types of food, some animals spend their lives eating only one type. The giant panda eats only one particular type of bamboo. Other animals eat only one type of food even when given the choice. A kind of white butterfly will stay on the leaves of a cabbage, even though there are plenty of other vegetables in the garden. However, most animals have a more varied diet. The bear eats fruits and fish. The fox eats small animals, birds and fruits. The diet of these animals will be different depending on the season.

Humans have a very varied（广泛的）diet. We often eat food because we like it and not because it is good for us. In countries such as France and Britain, people eat foods with too much sugar. This makes them overweight, which is bad for their health. Eating too much red meat and animal products, such as butter, can also be bad for the health. Choosing the right food, therefore, has become an area of study in modern life.

Keeping secrets is a burden

    “Don't tell anyone”. We hear these words when someone tells a secret to us. But it can be hard to keep a secret. We're often tempted to “spill the beans(说漏嘴)”, even if we regret it later.

    According to Asim Shah, professor in the Menninger Department of Psychiatry and Behavioral Sciences at Baylor College of Medicine, US, keeping a secret may well “become a burden”. This is because people often have an “obsessive and anxious urge to share it with someone”.

    An earlier study, led by Anita E. Kelly, a scientist at the University of Notre Dame, US, suggested that keeping a secret could cause stress. People entrusted(受委托的) with secrets can suffer from depression, anxiety, and body aches, reported the Daily Mail.

    But with secrets so often getting out, why do people share them at all? Shah explained that people often feel that it will help them keep a person as a friend. Another reason people share secrets is guilt over keeping it from someone close to them. A sense of distrust can develop when people who are close do not share it with each other. “Keeping or sharing secrets often puts people in a position of either gaining or losing the trust of someone,” according to Shah.

    He added that talkative people could let secrets slip out (泄露).But this doesn't mean that it is a good idea only to share secrets with quiet people. A quiet person may be someone who keeps everything inside. To tell such a person a secret may cause them stress, and make them talk about the secret. Shah said that to judge whether to tell someone a secret.

    Shah said that to judge whether to tell someone a secret, you'd better put yourself in their position. Think about how you would feel to be told that you mustn't give the information away. Shah also recommended that if you accidentally give up someone's secret you should come clean about it. Let the person know that their secret isn't so secret anymore.

    Many of us have had this experience: we lie down in a bed other than our own, perhaps at a friend's house or in a hotel room, and find it difficult or impossible to fall asleep. Is it because the bed is uncomfortable? Maybe, but perhaps there can be other reasons.

    According to a new study published in Current Biology, a significant reason is what the scientists call "first night effect". They believe that one side of the brain acts as a "night watch" to warn us about potential dangers. It forces us to stay awake on the first night in a new environments.

    For the study, 35 young volunteers were asked to sleep in a sleep lab for several days. Meanwhile, researchers watched their brain activities.

    According to the researchers, on their first night, the left brain was more active than the right brain and people had a hard time sleeping. However, left-brain activities decreased as days went by, falling even to the point of complete calm. In this process, the participants got an increasingly better sleep experience.

    The findings suggest that the different rhythms of the sides of the brain affect our sleep. When the two sides work differently, the balance between them is broken. Thus, the brain can't relax and is sensitive to anything strange in the surroundings, just as it is in the daytime.

    "At some level, the brain is continuing to analyze things, even though you are not aware of the analysis, " US professor Jerome Siegel told Smithsonian

    "If something unusual happens - if a door opens or you hear a key in a lock --you can be alert, even though the intensity of the stimulus (刺激强度) is quite low." More surprisingly, this phenomenon is similar to the way some animals sleep.

    The researchers think that it is the result of evolution (进化), and works to protect us in potentially dangerous environments.

    If you have ever had what you think is "first night effect", researchers suggest that you bring your own pillow or sleep in a room similar to your bedroom next time you sleep away from home.

    The Japanese have always been at the forefront at deploying (利用) robots to perform jobs that are traditionally done by humans. Over the past year, humanoid robots have been seen helping customers at the Mitsubishi Bank and even filling in for human science communicators at museums. Therefore, it is not surprising to hear that the country has the worlds first hotel that is staffed almost entirely by the Androids!

    The aptly (巧妙地) named Henn-na ("strange" in Japanese) Hotel which opened its doors on July 17 is located at Nagasaki's Huis Ten Bosch theme park. It is the idea of Hideo Sawada, a Japanese businessman who is fascinated by the possibility of replacing humans with robots. His aim is to have this futuristic hotel be run mainly by the intelligent humanoids.

    Guests checking-in are welcomed by a family friendly English-speaking robot wearing a bow tie and bell-hop (侍者) hat. Though experienced at his job, he does request guests not to ask him "a difficult question" since he is after all, "just a robot!" Those seeking a more "regular" experience, can approach the human-like Japanese-speaking robot.

    When ready, visitors can request the robot "porters" to help carry belongings to their room. Those that need to stow away valuables can hand them to a helpful robot who will place them inside an individual safe box in exchange for a small fee. A one-foot-high concierge (管理人) is available to provide information about the hotel's amenities (便利设施), nearby attractions, and even order a taxi if needed.

    So how much does it cost to live in this crazy cool hotel? It depends on when you decide to go. During the low season, guests can get away with paying as little $60 a night for a basic room. However, during the peak season when rates, are determined by an online auction, the price can get as high as $153.