The African elephant, which is the largest land animal remaining on earth, is of great importance to African ecosystem. Unlike other animals, the African elephant is to a great extent the builder of its environment. As a big plant-eater, it largely shapes the- forest-and-savanna (大草原) surroundings in which it lives, therefore setting the terms of existence for millions of other animals that live in its habitat.

    It is the elephant's great desire for food that makes it a disturber of the environment and an important builder of its habitat. In its continuous search for the 300 pounds of plants it must have every day, it kills small trees and under-bushes, and pulls branches off big trees. This results in numerous open spaces in both deep tropical forests and in the woodlands that cover part of the African savannas. In these open spaces are numerous plants in various stages of growth that attract a variety of other plant-eaters.

    Take the rain forests for example. In their natural state, the spreading branches overhead shut out sunlight and prevent the growth of plants on the forest floor. By pulling down trees and eating plants, elephants make open spaces, allowing new plants to grow on the forest floor. In such situations, the forests become suitable for large hoofed plant-eaters to move around and for small plant-eaters to get their food as well.

    What worries scientists now is that the African elephant has become an endangered species. If the elephant disappears, scientists say, many other animals will also disappear from vast areas of forest and savanna, greatly changing and worsening the whole ecosystem.

    Since 2013, Torobo, a robotic arm designed to test the limits of artificial intelligence, has had one ambition—to be admitted to the University of Tokyo. However, it has repeatedly failed. This year was no exception.

    In early November Torobo took an exam to prepare for an all-important standardized test. While Torobo's total score of 525 out of 950 was 14 points higher than in 2015，its standard score of 57.1% was slightly lower, because human students did better in the 2016 test.

    Though the score，which is higher than the national average, is enough to get the robot admitted to many other famous Japanese universities,
it falls short of the minimum required for the University of Tokyo.

    A closer analysis of the results showed that Torobo's newly programmed ability to solve complex physics problems helped increase its
year-over-year physics score from 46. 5% to 59%. The robot also dug deep into its database of information from textbooks and websites to obtain
an impressive 66.3% in world history. The average 60% scores acquired in the two math sections, were not too shabby either.

    But，while Torobo is able to handle knowledge-based questions and ones involving complex mathematical calculations, it has a hard time thinking independently. As a result, the robot is unable to fully understand multiple sentences and phrases to arrive at the logical conclusions required in the English language tests. This weakness was reflected in the weak oral and writing scores, which came in at 36.2% and 50.5%, respectively.

    Fortunately, after four tiring years, the robot's creators have decided to free Torobo from its annual test-taking suffering, the research team will instead focus on improving the robot's ability to pick out specific answers from massive sets of data—a skill that led to its excellent history scores. They believe the expertise(专业技术）will  help Torobo succeed as an industrial robot.

    Andy was still traveling in Spain when he realized he had to confirm (确认) his flight home with the airline company (航空公司). He was visiting Spain in order to improve his Spanish. When he was speaking to people face to face, he had no difficulty understanding what they said. However, when he was speaking on the phone, he still had a problem. Andy called the airline. And the clerk confirmed that his plane was leaving at nine o'clock three days from that day. She also told Andy to be at the airport two hours earlier in order to check in his luggage and get a seat.

    Since he was leaving in three days, Andy didn't lose any time. He visited as many places as he could. He thought that it would probably be a while before he had enough money again. He wished he could come back and spend a year in Spain.

    Too quickly, the final day arrived. Andy left early for the airport to arrive two hours before take-off. He hated to rush. He went to the clerk to show his ticket. The clerk looked at the ticket in surprise. "Why, sir, but your flight was at nine o'clock in the morning, and now it is eight in the evening." "But I confirmed my flight," insisted Andy. "Will I have to pay for another ticket?"

    "No, sir. However, the next flight out will be three days from now."

    Andy's look of shock turned to pleasure as he realized that now he could continue his vacation.

    For thousands of years comets have been a mystery to man. They travel across the sky very fast and have a bright “tail” of burning gas. The comet Tempel 1 has an orbit（轨道） far outside the orbit of the furthest planet in our solar system, Pluto. It has been there for 4.6 billion years, 133 million kilometers from Earth. Last week a little American spacecraft crashed into Tempel 1. The spacecraft had a camera and it took a photograph of the comet every minute before it finally crashed into its surface.

    The space mission to Tempel 1 cost $335 million and was called Deep Impact. The spacecraft was travelling at 37,000 kilometers per hour when it hit the comet and the crash completely destroyed the spacecraft. But before it hit the comet, the spacecraft took some amazing photographs. The last one was a close-up picture which the spacecraft took just 3 seconds before it crashed into the comet.

    “Right now we have lost one spacecraft,” said a delighted NASA engineer. Deep Impact was like a American Independence Day fireworks display. It took many years to plan and ended in an enormous explosion. 

    The spacecraft which crashed into the comet was made of copper and was the size of a washing machine. It was dropped from a mothership into the path of the comet and the mothership then photographed the cloud of ice, dust and organic chemicals that rose from the surface of the comet after the crash.

    The crash completely destroyed the spacecraft but nothing really happened to the comet: experts believe that the crash slowed the comet down by no more than 1/10,000 of a millimeter a second.The aim of the mission was to study for the first time the interior of a comet.

    The mothership was 480 km from the explosion and observed the crash and the explosion with instruments for 800 seconds. Seven satellites, including the Hubble space telescope, watched the moment of drama, and over the next day and night about 50 telescopes on Earth were watching the distant comet.

Life in the Clear

    Transparent animals let light pass through their bodies the same way light passes through a window. These animals typically live between the surface of the ocean and a depth of about 3,300 feet — as far as most light can reach. Most of them are extremely delicate and can be damaged by a simple touch. Sonke Johnsen, a scientist in biology, says, "These animals live through their life alone. They never touch anything unless they're eating it, or unless something is eating them."

    And they are as clear as glass. How does an animal become see­through? It's trickier than you might think.

    The objects around you are visible because they interact with light.  Light typically travels in a straight line. But some materials slow and scatter (散射) light, bouncing it away from its original path. Others absorb light, stopping it dead in its tracks.  Both scattering and absorption make an object look different from other objects around it, so you can see it easily.

    But a transparent object doesn't absorb or scatter light, at least not very much. Light can pass through it without bending or stopping. That means a transparent object doesn't look very different from the surrounding air or water. You don't see it — you see the things behind it.

    To become transparent, an animal needs to keep its body from absorbing or scattering light. Living materials can stop light because they contain pigments (色素) that absorb specific colors of light. But a transparent animal doesn't have pigments, so its tissues won't absorb light. According to Johnsen, avoiding absorption is actually easy. The real challenge is preventing light from scattering.

    Animals are built of many different materials — skin, fat, and more — and light moves through each at a different speed. Every time light moves into a material with a new speed, it bends and scatters. Transparent animals use different tricks to fight scattering. Some animals are simply very small or extremely flat.  Without much tissue to scatter light, it is easier to be see­through. Others build a large, clear mass of non­living jelly­lie (果冻状的) material and spread themselves over it.

    Larger transparent animals have the biggest challenge, because they have to make all the different tissues in their bodies slow down light exactly as much as water does. They need to look uniform. But how they're doing it is still unknown. One thing is clear for these larger animals, staying transparent is an active process.  When they die, they turn a non­transparent milky white.

Best Way to Save Money

    Although the best way to save money can vary from person to person, depending on age, family size and other characteristics, there are still some easy things that all shoppers can do to keep more money in their bank accounts.

    Avoid Impulse (冲动的) Purchases

    When you shop, a best way to save money is to have a plan in mind to help you avoid impulse purchases. For instance, you might leave your credit cards at home and only carry the exact amount of cash that you will need for your planned purchase. Some shoppers agree to discuss any purchases over a certain dollar amount with their spouses (配偶) first.

    Know When to Pay for Quality

    Sometimes the best way to save money in the long term is to spend a little more money right now. A good piece of furniture can stay in the family for decades. A high-quality pair of shoes will last longer than a bargain pair and prevent foot pain. Leaner cuts of meat and organic produce provide health benefits for your family.

    Buy Secondhand

    Check classified ads, thrift stores and garage sales for used clothing, toys, furniture, and much more available at a part of their original cost. For the most secondhand savings, check out groups like Freecycle where members offer unwanted items for free to anyone willing to pick them up.

    Borrow Instead of Buy

    If you're only going to use something once, try to borrow it instead of spending your money on it. Borrow a tool from your neighbor. Swap books with a friend. Check out the resources at your local library. You'll also be reducing disorder in your home.