He paused, waiting for her to digest the information. withhold exchange understand contact

Rumors began to circulate about his financial problems. send hear confirm spread

The contract between the two companies will expire soon. shorten end start resume

She came across three children sleeping under a bridge. found by chance passed by took a notice of woke up

There was something peculiar in the way he smiles. different strange wrong funny

Black Holes 1. Black holes can be best described as a sort of vacuum, sucking up everything in space. Scientists have discovered that black holes come from an explosion of huge stars. Stars that are near death can no longer burn due to loss of fuel, and because its temperature can no longer control the gravitational(重力的)force, hydrogen ends up putting pressure onto the star’s surface until it suddenly explodes then collapses. 2. Black holes come from stars that are made of hydrogen, other gases and a few metals. When these explode it can turn into a stellar-mass(恒星质量)black hole, which can only occur if the star is large enough(should be bigger than the sun)for the explosion to break it into pieces, and the gravity starts to compact every piece into the tiniest particle. Try to see and compare: if a star that’s ten times the size of the sun end up being a black hole that’s no longer than 70 kilometers, then the Earth would become black hole that’s only a fraction of an inch! 3. Objects that get sucked in a black hole will always remain there, never to break free. But remember that black holes can only gobble up(吞噬)objects within a specific distance to it. It’s possible for a large star near the sun to become a black hole, but the sun will continue to stay in place. Orbits(轨道)do not change because the newly formed black hole contains exactly the same amount of mass as when it was a star, only its mass is totally contracted that it can end up as no bigger than a state. 4. So far, astronomers have figured out that black holes exist because of Albert Einstein’s theory of relativity. In the end, through numerous studies, they have discovered that black holes truly exist. Since black holes trap light and do not give off light, it is not possible to detect black holes via a telescope. But astronomers continue to explore galaxies(银河系), space and the solar system to understand how black holes might evolve. It is possible that black holes can exist for millions of years, and later contribute further process in galaxies, which can eventually lead to creation of new entities. Scientists also credit black holes as helpful in learning how galaxies began to form. A. What are black holes made of? B. Is there proof that black holes really exist? C. How were black holes named? D. How are black holes formed? E. What are different types of black holes? F. What happens to the objects around a black hole?

A. a fraction of an inch B. the creation of new entities C. the same amount of mass D. the tiniest particle E. an explosion of huge stars F. the existence of black holes

Putting Plants to Work Using the power of the sun is nothing new. People have had solar-powered calculators and buildings with solar panels(太阳能电池板)for decades. But plants are the real experts. They’ve been using sunlight as an energy source for billions of years. Cells in the green leaves of plants work like tiny factories to convert sunlight, carbon dioxide(二氧化碳), and water into sugars and starches(淀粉), stored energy that the plants can use. This conversion process is called photosynthesis(光合作用). Unfortunately, unless you’re a plant, it’s difficult and expensive to convert sunlight into storable energy. That’s why scientists are taking a closer look at exactly how plants do it. Some scientists are trying to get plants, or biological cells that act like plants, to work as very small photosynthesis power stations. For example, Maria Ghirardi of the National Renewable Energy Laboratory in Golden. Colo., is working with green algae(水藻). She’s trying to trick them into producing hydrogen instead of sugars when they perform photosynthesis. Once the researchers can get the algae working efficiently, the hydrogen that they produce could be used to power fuel cells in cars or to generate electricity. The algae are grown in narrow-necked glass bottles to produce hydrogen in the lab. During photosynthesis, plants normally make sugars or starches.“ But under certain conditions, a lot of algae are able to use the sunlight energy not to store starch, but to make hydrogen.“ Ghirardi says. For example, algae will produce hydrogen in an airfree environment. It’s the oxygen in the air that prevents algae from making hydrogen most of the time. Working in an airfree environment, however, is difficult. It’s not a practical way to produce cheap energy. But Ghirardi and her colleagues have discovered that by removing a chemical called sulfate(硫酸盐)from the environment that the algae grow in, they will make hydrogen instead of sugars, even when air is present. Unfortunately, removing the sulfate also makes the algae’s cells work very slowly, and not much hydrogen is produced. Still, the researchers see this as a first step in their goal to produce hydrogen efficiently from algae. With more work, they may be able to speed the cells’ activity and produce larger quantities of hydrogen. The researchers hope that algae will one day be an easy-to-use fuel source. The organisms are cheap to get and to feed, Ghirardi says, and they can grow almost anywhere: “You can grow them in a reactor, in a pond. You can grow them in the ocean. There’s a lot of flexibility in how you can use these organisms.“

On the Trail of the Honey Badger On a recent field trip to the Kalahari Desert, a team of researchers learnt a lot more about honey badgers(獾). The team employed a local wildlife expert, Kitso Khama, to help them locate and follow the badgers across the desert. Their main aim was to study the badgers’ movements and behavior as discreetly(谨慎地)as possible without frightening them away or causing them to change their natural behavior. They also planned to trap a few and study them close up before releasing them in view of the animal’s reputation, this was something that even Khama was reluctant to do. “The problem with honey badgers is they are naturally curious animals, especially when they see something new.“ he says. “That, combined with their unpredictable nature, can be a dangerous mixture. If they sense you have food, for example, they won’t be shy about coming right up to you for something to eat. They’re actually quite sociable creatures around humans, but as soon as they feel they might be in danger, they can become extremely vicious(凶恶的). Fortunately this is rare, but it does happen.“ The research confirmed many things that were already known. As expected, honey badgers ate any creatures they could catch and kill. Even poisonous snakes, feared and avoided by most other animals, were not safe from them. The researchers were surprised, however, by the animal’s fondness for local melons, probably because of their high water content. Previously researchers thought that the animal got all of its liquid requirements from its prey(猎物). The team also learnt that, contrary to previous research findings, the badgers occasionally formed loose family groups. They were also able to confirm certain results from previous research, including the fact that female badgers never socialised with each other. Following some of the male badgers was a challenge, since they can cover large distances in a short space of time. Some hunting territories cover more than 500 square kilometers. Although they seem happy to share these territories with other males, there are occasional fights over an important food source, and male badgers can be as aggressive towards each other as they are towards other species. As the badgers became accustomed to the presence of people, it gave the team the chance to get up close to them without being the subject of the animals’ curiosity—or a sudden aggression. The badgers’ eating patterns, which had been disrupted, to normal. It also allowed the team to observe more closely some of the other creatures working associations with the honey badger, as these seemed to badgers’ relaxed attitude when near humans.

Come out, or I’ll bust the door down. shut break set beat

As a politician, he knows how to manipulate public opinion. express divide influence voice

He paused, waiting for her to digest the information. withhold exchange understand contact

Make sure the table is securely anchored. repaired cleared booked fixed

It seemed incredible that he had been there a week already. right unbelievable obvious unclear

The rules are too rigid to allow for human error. general inflexible complex direct

Why India Needs Its Dying Vultures The vultures(秃鹰)in question may look ugly and threatening, but the sudden sharp decline in three species of India’s vultures is producing alarm rather than celebration, and it presents the world with a new kind of environmental problem. The dramatic【C1】______in vulture numbers is causing widespread disruption to people living in the【C2】______areas as the birds. It is also causing serious public health problems【C3】______the Indian subcontinent. While their reputation and appearance may be unpleasant to many Indians, vultures have【C4】______played a very important role in keeping towns and villages all over India【C5】______. It is because they feed on dead cows. In India, cows are sacred animals and are【C6】______left in the open when they die in their thousands upon thousands every year. The disappearance of the vultures has【C7】______an explosion in the numbers of wild dogs feeding on the remains of these【C8】______animals. There are fears that rabies(狂犬症)may increase as a result. And this terrifying disease may ultimately(最终)affect humans in the region,【C9】______wild dogs are its main carriers. Rabies could also spread to other animal species,【C10】______an even greater problem in the future. The need for action is【C11】______, so an emergency project has been launched to find a solution to this serious vulture problem. Scientists are trying to【C12】______the disease causing the birds’ deaths and, if possible, develop a cure. Large-scale vulture【C13】______were first noticed at the end of the 1980s in India. A population survey at that time showed that the three species of vultures had declined【C14】______over 90 per cent. All three species are now listed as “critically endangered“. As most vultures lay only single eggs and【C15】______about five years to reach maturity, reversing their population decline will be a long and difficult exercise.

She gets aggressive when she is drunk. offensive worried sleepy anxious

I have little information as regards her fitness for the post. about at with from

These animals migrate south annually in search of food. explore inhabit prefer travel

The police will need to keep a wary eye on this area of town. naked blind cautious private

He was tempted by the high salary offered by the company. taught kept changed attracted