1 . Monkeys seem to have a way with numbers.

A team of researchers trained three Rhesus monkeys to associate 26 clearly different symbols consisting of numbers and selective letters with 0-25 drops of water or juice as a reward. The researchers then tested how the monkeys combined—or added—the symbols to get the reward.

Here’s how Harvard Medical School scientist Margaret Livingstone, who led the team, described the experiment: In their cages the monkeys were provided with touch screens. On one part of the screen, a symbol would appear, and on the other side two symbols inside a circle were shown. For example, the number 7 would flash on one side of the screen and the other end would have 9 and 8. If the monkeys touched the left side of the screen they would be rewarded with seven drops of water or juice; if they went for the circle, they would be rewarded with the sum of the numbers—17 in this example.

After running hundreds of tests, the researchers noted that the monkeys would go for the higher values more than half the time, indicating that they were performing a calculation, not just memorizing the value of each combination.

When the team examined the results of the experiment more closely, they noticed that the monkeys tended to underestimate(低估) a sum compared with a single symbol when the two were close in value—sometimes choosing, for example, a 13 over the sum of 8 and 6. The underestimation was systematic: When adding two numbers, the monkeys always paid attention to the larger of the two, and then added only a fraction(小部分) of the smaller number to it.

“This indicates that there is a certain way quantity is represented in their brains, ”Dr. Livingstone says. “But in this experiment what they’re doing is paying more attention to the big number than the little one.”

I'm not sure     1     is more frightened, me or the female gorilla(大猩猩）that suddenly appears out of nowhere. I'm walking on a path in the forest in the Central African Republic. Unexpectedly, I'm face-to-face with the gorilla, who begins screaming at     2     top of her lungs. That makes her baby scream, and then a 400-pound male appears. He screams the

    3    (loud)of all. The noise shakes the trees as the male beats his chest and charges toward me. I quickly lower myself, ducking my head to avoid     4    (look) directly into his eyes so he doesn't feel    5    (challenge).

My name is Mireya Mayor. I'm a     6    (science)who studies animals such as apes and monkeys. I was searching     7     these three western lowland gorillas I'd been observing. No one had seen them for hours, and my colleagues and I were worried.

When the gorillas and I frightened each other, I was just glad to find     8    (they) alive. True to a gorilla's unaggressive nature, the huge animal     9    (mean)me no real harm. He was just saying: "I'm king of this forest, and here is your reminder!" Once his message was delivered, he allowed me     10     (stay)and watch.

4 . Let's take a minute to think about the water we use. The human body is 60% water and we need to drink lots of water to be healthy. When we are thirsty we just go to the kitchen and fill a glass with clean water.

    1    For example, farmers, who produce the food we eat, use water to make the plants grow. When we turn on a light or switch on a TV or a computer we use energy and we need water to produce this energy.

The truth is that we are lucky enough to have clean water whenever we want，but this is not the case for many people around the world.    2    That's around one in 10 people in the world. If we drink dirty water，we can catch diseases from the bacteria and become ill. Every year over 500，000 children die from diarrhea(腹泻)from dirty water. That's around 1，400 children every day！Also，in some countries children walk many kilometres every day to get water.    3    Therefore，they don't have time to learn how to read or write and don't get an education.

    4    On this day every year，countries around the world hold events to educate people about the problems of dirty water and that clean water is something that everyone should have around the world. At one school in the UK，children between the ages of 10 and 15 walk 6km with six litres of water.    5    People give them money to do this and all the money helps get clean water to as many people as possible around the world.

5 . California has lost half its big trees since the 1930s, according to a study to be published Tuesday and climate change seems to be a major factor(因素).

The number of trees larger than two feet across has declined by 50 percent on more than 46, 000 square miles of California forests, the new study finds. No area was spared or unaffected, from the foggy northern coast to the Sierra Nevada Mountains to the San Gabriels above Los Angeles. In the Sierra high country, the number of big trees has fallen by more than 55 percent; in parts of southern California the decline was nearly 75 percent.

Many factors contributed to the decline, said Patrick McIntyre, an ecologist who was the lead author of the study. Woodcutters targeted big trees. Housing development pushed into the woods. Aggressive wildfire control has left California forests crowded with small trees that compete with big trees for resources(资源).

But in comparing a study of California forests done in the 1920s and 1930s with another one between 2001 and 2010, McIntyre and his colleagues documented a widespread death of big trees that was evident even in wildlands protected from woodcutting or development.

The loss of big trees was greatest in areas where trees had suffered the greatest water shortage. The researchers figured out water stress with a computer model that calculated how much water trees were getting in comparison with how much they needed, taking into account such things as rainfall, air temperature, dampness of soil, and the timing of snowmelt(融雪).

Since the 1930s, McIntyre said, the biggest factors driving up water stress in the state have been rising temperatures, which cause trees to lose more water to the air, and earlier snowmelt, which reduces the water supply available to trees during the dry season.

8 . Many cities around the world today are heavily polluted. Careless methods of production and ________ of consumer demands for environment friendly products have ________ the pollution problem. One ________ is that millions of tons of glass, paper, plastic, and metal containers are produced, and these are difficult to get rid of.

________, today, more and more consumers are choosing “green” and demanding that the products they buy should be safe for the environment. ________ they buy a product, they ask questions like these: “Will this shampoo damage the environment?” “Can this metal container be ________ or can it only be used once?”

A recent study showed that two ________ five adults now consider the environmental safety of a product before they buy it. This means that companies must now change the ________ they make and sell their products to make sure that they are “green,” that is, friendly to the environment.

Only a few years ago, it was impossible to find green products in supermarkets, but now there are hundreds. Some supermarket products ________ labels to show that the product is green. Some companies emphasize that their products are clean and safe in their advertising and have made it their main selling ________.

The ________ for a safer and cleaner environment is making companies rethink ________ they do business. No longer will the public accept the old ________ of “Buy it, use it, throw it away and forget it.” The public ________ is still here, and companies are ________ their act gradually.

9 . Rainforests are home to a rich variety of medicinal plants, food, birds and animals. Can you believe that a single bush（灌木丛）in the Amazon may have more species of ants than the whole of Britain! About 480 varieties of trees may be found in just one hectare of rainforest.

Rainforests are the lungs of the planet-storing vast quantities of carbon dioxide and producing a significant amount of the world's oxygen. Rainforests have their own perfect system for ensuring their own survival; the tall trees make a canopy（树冠层）of branches and leaves which protect themselves, smaller plants, and the forest animals from heavy rain, intense dry heat from the sun and strong winds.

Amazingly, the trees grow in such a way that their leaves and branches, although close together, never actually touch those of another tree. Scientists think this is the plants' way to prevent the spread of any tree diseases and make life more difficult for leaf-eating insects like caterpillars. To survive in the forest, animals must climb, jump or fly across the gaps. The ground floor of the forest is not all tangled leaves and bushes, like in films, but is actually fairly clear. It is where dead leaves turn into food for the trees and other forest life.

They are not called rainforests for nothing! Rainforests can generate 75%of their own rain. At least 80 inches of rain a year is normal-and in some areas there may be as much as 430 inches of rain annually. This is real rain-your umbrella may protect you in a shower, but it won't keep you dry if there is a full rainstorm. In just two hours, streams can rise ten to twenty feet. The humidity（湿气）of large rainforests contributes to the formation of rainclouds that may travel to other countries in need of rain.