请阅读下列短文, 从短文后各题所给的 A、B、C、D 四个选项中, 选出最佳选项

    The sound of a mosquito can mean trouble in many parts of the world. The bite of the mosquito can be deadly. The insects carry serious diseases like malaria (疟疾). It is estimated that almost 630,000 people died from malaria and malaria­related causes in 2012, and most of these cases were in African countries.

    In the United States, a group of California scientists are working to develop a more effective and less costly substance (物质) to protect people from mosquitoes. The researchers are investigating the sense of smell in mosquitoes. They found the insects use the same receptor for identifying carbon dioxide in human breath as they do for the smell of our skin. Anandasankar Ray, who is leading the investigation, says scientists tested more than a million chemical compounds (化合物) until they found a substance called Ethyl Pyruvate. He says Ethyl Pyruvate makes the mosquitoes' receptors inactive. “When we apply Ethyl Pyruvate to a human arm and offer it to hungry mosquitoes in a cage, very few of the mosquitoes are attracted to the human arm because only a few of them are able to smell it out,” said Ray.

    Genevieve Tauxe, a member of the research team, says it was not easy to find the neurons (神经元) of noble cells that recognize both the smell of human breath and skin. “With the device used to examine the mosquito, we are able to insert a very small electrode (电极) into the part of the mosquito's nose, where its smelling neurons are and where the smell is happening,” said Tauxe.

    Anandasankar Ray says a product based on Ethyl Pyruvate may cost less to produce than DEFT, the most effective chemical treatment now in use. He says DEFT is too costly for most people who live in areas affected by malaria.

    “Perhaps by finding smells that can attack other target receptors, we will be able to improve upon DEFT and finally have the next generation of insect behaviour control products,” said Ray.

    Mrs. Strickland did not talk much, but she had a pleasant gift for keeping the conversation general; and when there was a pause she threw in just the right remark to set it going once more.

    "Why do nice women marry dull men?"

    "Because intelligent men won't marry nice women. "

    Mrs. Strickland had the gift of sympathy.

    There was another thing I liked in Mrs. Strickland. She managed her surroundings with elegance(优雅). Her flat was always neat and cheerful with flowers. The meals in the little dining room were pleasant; the table looked nice; the food was well cooked. It was impossible not to see that Mrs. Strickland was an excellent housekeeper. And you felt sure that she was an admirable mother. There were photographs in the drawing room of her son and daughter. The son—his name was Robert—was a boy of sixteen at Rugby. He had his mother's fine eyes. He looked clean, healthy, and normal.

    “I don't know that he's very clever,” she said one day, when I was looking at the photograph, “but I know he's good. He has a charming character.”

    The daughter was fourteen. Her hair, thick and dark like her mother's, fell over her shoulders, and she had the same kindly expression and untroubled eyes.

    “They both look like you,” I said.

    “Yes, I think they are more like me than their father.”

    “Why have you never let me meet him?” I asked.

    “Would you like to?” she smiled and her smile was really very sweet.

    “You know, he's not at all literary,” she said. “He has no interest in literature.”

    “He's on the Stock Exchange(证券交易所), and he's a typical broker(经纪人). I think he'd bore you to death.”

    “Does he bore you?” I asked.

    “You see, I happen to be his wife. I'm very fond of him.” She smiled to cover her shyness, and her eyes grew tender.

    “He doesn't pretend to be a talent. He doesn't even make much money on the Stock Exchange. But he's awfully good and kind.”

    “I think I should like him very much.”

    “I'll ask you to dine with us quietly some time, but mind, you come at your own risk; don't blame me if you have a very dull evening.”

【1】A safari park is a park in which wild animals are kept. They are mainly located in east or central Africa. They often occupy a very wild area, with mountains and rivers. To visit the park and look at the animals, people have to drive around in a car for a few of hours because the park is huge.

【2】In south Africa there is a safari park, which contains all sorts of wild animals like lions, elephants, rhinoceroses(犀牛), zebras, wild pigs, deer and giraffes.

【3】There is a wild road leading through the park, but nobody is permitted to walk on the road. Anyone traveling in the park has to go in a car because wild animals may fiercely attack people. From the car he may see almost every types of African wildlife. Some of these are getting scarce (稀有的) because people kill them for various reasons. For example, rhinoceroses are killed for their horns (角), which are used in traditional Chinese medicines for colds and headaches. Perhaps they will be seen only in museums and books one day.

【4】Travels may buy food for the animals. They can feed them when they tour the park. Of course, they should not feed them in a close distance because the wild animals may attack people. In addition, they should only give proper food to the animals.

【5】A traveler may carry a gun with him in his journey. The gun is given to him by the government. However, it is not used for hunting. In fact, a seal(封条) is fixed to it. The traveler may fire at a wild beast to defend himself in case he is attacked. However, he has to prove to the government that he has been attacked and that he has not fired at a harmless animal.

    Believe it or not, the size of the human brain has become smaller over the past 20,000 years. Scientists argue over whether this means we are becoming more or less intelligent as a species.

    “I'd call that a major downsizing in an evolutionary eye blink (眨眼),” John Hawks told Discover magazine.

    Why is the brain becoming smaller?

    There are different theories to explain it. One is that tens of thousands of years ago, before the decline began, to survive in cold and dangerous conditions, humans needed a stronger and larger body and therefore, a larger head. Also they had to chew the tough meat of rabbits, foxes and horses. As conditions improved, the brain stopped growing, according to supporters of this theory.

    Another theory comes from a recent study by David Geary and Drew Bailey. They found that brain size decreased as population density(密度) increased.

    “As complex societies appeared, the brain became smaller because people did not have to be as smart to stay alive.” Geary told AFP.

    But smaller brain size does not necessarily mean that modern humans are less smart than their ancestors. “Modern humans simply developed different, more complex forms of intelligence,” said Brian Hare.

    Hare's studies focus on two types of great apes: chimpanzees and bonobos. Both are much like humans, but are physically quite different from one another. The bonobo has a smaller brain than the chimpanzee, and is also much less aggressive and more tolerant.

    “When it comes to working out a problem,” Hare said, “chimpanzees are much less likely to accomplish it if it involves working together. Not so with bonobos.”

The smaller brain in modern humans may be evidence that we can cooperate,” Hare told the US National Public Radio.

    British children used to play conkers (板栗游戏) in the autumn when the horse-chestnut trees started to drop their shiny brown nuts. They would select a suitable chestnut, drill a hole in it and thread it onto a string, then swing their conker at that of an opponent until one of them broke. But the game has fallen out of favour. Children spend less time outdoors and rarely have access to chestnut trees. Besides, many schools have banned conkers games, worried that they might cause injuries or nut allergies.

    That sort of risk-averseness(规避风险) now spreads through every aspect of childhood. Playgrounds have all the excitement designed out of them to make them safe. Many governments, particularly in societies such as America, have tightened up their rules, requiring parents to supervise(监管) young children far more closely than in the past. Frank Furedi of the University of Kent, a critic on modern parenting, argues that allowing children to play unsupervised or leaving them at home alone is increasingly described as a symptom of irresponsible parenting.

    In part, such increased caution is a response to the huge wave of changes. Large-scale urbanization, smaller and more mobile families, the move of women into the labor market and the digitization of many aspects of life have unavoidably changed the way that people bring up their children. There is little chance that any of these trends will be changed, so today's more intensive(精细化 ) parenting style is likely to go on.

    Such parenting practices now embraced by wealthy parents in many parts of the rich world, particularly in America, go far beyond an adjustment to changes in external conditions. They mean a strong bid to ensure that the advantages enjoyed by the parents' generation are passed on to their children. Since success in life now turns mainly on education, such parents will do their best to provide their children with the schooling, the character training and the social skills that will secure access to the best universities and later the most attractive jobs.

    To some extent that has always been the case. But there are more such parents now, and they are competing with each other for what economists call positional goods. This competition starts even before the children are born. The wealthy classes will take their time to select a suitable spouse and get married, and will start a family only when they feel ready for it.

    Children from less advantaged backgrounds, by contrast, often appear before their parents are ready for them. In America 60% of births to single women under 30 are unplanned, and over 40% of children are born outside marriage. The result, certainly in America, has been to widen already massive social inequalities yet further.

    All the evidence suggests that children from poorer backgrounds are at a disadvantage almost as soon as they are born. By the age of five or six they are far less "school-ready" than their better-off peers, so any attempts to help them catch up have to start long before they get to school. America has had some success with various schemes involving regular home visits by nurses or social workers to low-income families with new babies. It also has long experience with programmes for young children from poor families that combine support for parents with good-quality child care. Such programmes do seem to make a difference. Without extra effort, children from low-income families in most countries are much less likely than their better-off peers to attend preschool education, even though they are more likely to benefit from it. And data from the OECD's PISA programme suggest that children need at least two years of preschool education to perform at their best when they are 15.

    So the most promising way to ensure greater equality may be to make early-years education and care for more widely available and more affordable, as it is in the Nordics. Some governments are already rethinking their educational priorities, shifting some of their spending to the early years.

    Most rich countries decided more than a century ago that free, compulsory education for all children was a worthwhile investment for society. There is now an argument for starting preschool education earlier, as some countries have already done. In the face of crushing new inequalities, a modern version of that approach is worth trying.