Experiments under way in several labs aim to create beneficial types of genetically modified foods, including starchier potatoes and caffeine-free coffee beans. Genetic engineers are even trying to transfer genes from a cold-winter fish to make a frost-resistant tomato.

    A low-sugar GM strawberry now in the works might one day allow people with health problems such as diabetes (糖尿病) to enjoy the little delicious red fruits again. GM beans and grains rich in protein(蛋白质) might help people at risk of developing kwashiorkor. Kwashiorkor, a disease caused by severe lack of protein, is common in parts of the world where there are severe food shortages.

    Commenting on GM foods, Jonathon Jones, a British researcher, said: "The future benefits will be enormous（巨大的）, and the best is yet to come". To some people, GM foods are no different from unmodified foods. "A tomato is a tomato," said Brian Sansoni, an American food manufacturer.

    Critics of GM foods challenge Sansoni's opinion. They worry about the harm that GM crops might do to people, other animals, and plants.

    In a recent lab study conducted at Cornell University, scientists tested pollen(花粉) made by BT corn, which makes up one-fourth of the U.S. corn crop. The scientist dropped the pollen onto milkweed, a plant that is the only known food source of a butterfly caterpillar(毛虫). Within four days of feeding on the leaves, almost half of a test group of caterpillars died. "This is a warning bell." said Cornell researcher Linda Raynor.

    Some insects that are not killed by GM foods might find themselves made stronger. How so? The insecticides are used on the crops to kill the pests. But GM plants produce a continuous level of insecticide. Insects relying on those crops may develop resistance to the plants and they may also develop a resistance to the insecticide.

    At the forum on GM food held last year in Canada. GM crops that have been made resistant to the herbicide might crossbreed with wild plants, creating "superweeds" that could take over whole fields.

    So where do you stand? Should GM food be banned in the United States, as they are in parts of Europe? Or do their benefits outweigh（胜过） any of the risks they might carry?

    Climbing Without Ropes

    The popular image of the mountain climber is of a person carefully climbing a steep cliff with a network of safety ropes, but it is not the only kind. Many climbers now enjoy bouldering. It's more accessible and better for the environment.

    Here is an example of a climber addressing a bouldering problem.

    Figure 1: The climber has two routes she could take, one to the left and one to the right. The left one appears easier because it has a jug within easy reach, but look what happens if she chooses that direction. She gets stuck on the rock and has to go back down. Sometimes that is even more difficult than going up.

    Figure 2: The climber takes the one to the right this time. Using a foothold and placing her right hand in a crimp, she is able to lift herself up and locate other handholds. After only a few moves, she is able to throw her leg over the top of the boulder and pull herself up.

    I remember the day when I first learned to ride a bike. It was a frightening, yet fun experience. My granddad was the one who taught me, and he helped me when I got hurt. The first time I got on a bike, I had no idea what I was doing, and just about everything went wrong. My granddad told me to just put my feet on the pedals and start, pedaling(骑自行车). He also told me he would hold onto the back of the bike the whole time, yet he didn't.

    As soon as I started trying to balance myself, he let go. I happened to look back just then.  I was scared to death that I was going to fall and hurt myself. When I was scared, my mind went blank from pedaling, and I just wanted off. I forgot how to use the brakes(车闸) and fell right off the bike. My granddad kept encouraging me to get up and try again, and after about 15 minutes, I finally stopped crying, got up and tried again.

    As soon as I started pedaling again, my pants got caught in the chain, and I fell flat on my face and hit my nose. Since that happened, my granddad decided to call it a day and try again the next morning. The next morning I woke up bright and early, and was very eager to try to ride my bike. My nose felt better, so I wasn't that afraid of falling anymore.

    Though I knew there were a lot of difficulties on the way to mastering the skills in riding a bike, l believed I could do well with my granddad's help. After all, riding a bike was what I wanted to do eagerly.

    Wolves travel shorter distances and move slower during snowfall events, according to new research by University of Alberta biologists. The effects were most pronounced at night, when wolves hunt, and behaviour returned to normal within a day. Wolf tracks across snow in northeastern Alberta.

    "Our findings suggest that there is something about actively falling snow that causes wolves to slow down," said Amanda Droghini, a former MSc student in the Department of Biological Science and lead author on the study. "We don't know the exact mechanism behind that. It's unlikely that they were staying still because they were feasting on a recent kill. Instead, active precipitation(降雪量)might affect wolves' hunting abilities. Like rain, snow clears the air column of scent molecules. So, maybe falling snow makes it harder for wolves to detect the smell of prey."

    Over the course of two winters, the researchers used remote cameras to disclose snowfall events and estimate snow depth. To study wolf movement, they collected telemetry(测距仪) data from 17 wolves to calculate travel speed and duration, as well as resting periods. It is the first study to examine how large flesh-eating animals respond to snowfall events.

    With the effects of climate change on precipitation in the north forest region uncertain, it is difficult to predict the implications for wolf populations. Studies such as these increase our understanding of how large mammals react to normal snowfall events, but the type and amount of winter precipitation will likely have an impact on animal behavior and the energetic cost of movement.

    "Winter is already challenging for many wildlife species because moving through snow requires more energy. Snow can also make it harder for animals to access food resources," said Droghini, who conducted the research under the supervision of Professor Stan Boutin, Alberta Biodiversity Conservation Chair.

    "Anything that increases those costs, such as increased rain-on-snow events, could lead to lacking in nutrition, poor body condition, and even starvation as animals are unable to make up for those additional costs. That is one of the worst-case scenarios(设想)but, in truth, we know very little about potential changes to precipitation patterns and how wildlife will respond to those changes."

    You can tell a lot about a country by what's on its television sets. Britain's TV screens are completely steeped in class, and have long been so.

    From laughing at poor people in reality shows to laughing at posh people in Downton Abbey, this is how Britain likes to unwind in the evening: by laughing at other classes, and laughing at people for laughing about class.

    Like it or loathe it, many see the class system as a quite essential element of British life, together with our obsession for tea and cake and talking about the weather.

    Whether you are a lord, a lady, or just the king of your own middle class kingdom, everyone in the UK fits into the class system. How the class system works is a hard question even for a British person to answer.

    There are four main groups in the British class system: lower, working, middle and upper class. Although recently the BBC has tried to confuse everyone even more by adding three more categories.

    The British are very aware of class; it is often said that we have an in-built 'class radar'; we pick up on subtle social clues which indicate which class a person comes from. Class is not just about your job, where you live and how much you earn. It's about who you are.

Anyone keen to view from on high the prosperous cityscape of Guangdong, may soon can do so from the cabin of a flying taxi. On October 13th the Civil Aviation (航空) Administration of China (CAAC) awarded a "type certificate" to the world's first electric vertical take-off and landing (eVTOL)taxi. And the small two-seater, called the EH216-S, was also permitted to fly without a pilot on board.

The EH216-s is made by EHang, a company based in Guangdong. It looks like a large consumer drone with a passenger bubble installed on top. Propulsion (推动力) is provided by 16 small rotors (转子), installed on the tips of eight arms that fold away when the vehicle is not in use, allowing it to park in small spaces.

The CAAC gave its approval after EHang had conducted more than 40,000 test flights, including with volunteer passengers in 18 cities across China. It also monitored the EH216-s to structural analysis and crash tests, and checked its ability to keep flying if one of its rotors fails. Regulators (监管机构) also inspected the wireless network EHang uses to link its flying taxis to a control centre on the ground. That allows backup pilots to land an aircraft by remote control if there is a problem.

EHang says its pilotless eVTOLs will be quieter than helicopters and much cheaper to operate, thanks to the ability to swap out an expensive pilot for a second paying passenger. The firm also thinks that doing away with pilots will make things safer. A computer's attention never swings, and its reaction operate at a high speed. And it is much easier to automate than driving,for there are fewer barriers and unexpected situations to navigate.

EHang has ambitions beyond China, too. It has carried out demonstration flights in Amèrica and Europe with the aim of obtaining type certificates in both markets. But their regulators both have signalled that they will allow autonomous flights only after the vehicles have proved themselves safe in human hands.