When Millet was a boy he worked on his needy father's farm. At the rest hour in the fields the other workers would all take naps (打盹儿），but young Millet would spend time drawing. Finally the village where he lived gave him a little money to Paris to study art.

When Millet reached Paris, he had a tough time. Fortunately, when he was almost starving, someone bought one of his peasant paintings, which enabled his family to leave for Barbizon.

Millet's pictures of peasants at work were painted in a unique way. The painter would go out on the farms and watch them carefully, then he would come home and paint what he had seen. So astonishingly accurate was his memory that he could paint at home without models and get all the movements of his figures right. When he did need a figure to go by he would ask his wife to pose for him.

One of his noted artworks is called "The Sower", which shows a man seeding. He reaches into his bag for seed and then swings backward to scatter (撒播） the seed, and with each swing of his hand the sower strides (大步走） forward. In Millet's picture the sower has been working hard, but his swinging step and arm still move smoothly, like a machine. Only the man's head reveals his great tiredness.

Another masterpiece is called "The Gleaners". A gleaner is someone picking up the leftover in the field after the wheat harvest. When farmers near Barbizon are extremely badly-off, even the little the gleaners can find is a help. You can see from Millet's picture what back-breaking work gleaning must be.

England and Wales launched a COVID-19 smartphone app on Thursday, allowing users to trace contacts, check the local level of risk and record visits to places such as pubs, four months after the technology was promised to the public.

The NHS COVID-19 app comes as Britain prepares for a second wave of infections, with daily case numbers rising at rates not seen since the peak of the pandemic (流行病）and a testing system unable to cope with demand in many areas.

The government had said a COVID-19 app would arrive in May, but early trials were troubled by problems, and developers abandoned home-grown technology in favor of Apple and Google's model in June.

As the delay lengthened, the governmentdownplayedthe importance of smartphones in fighting COVID-19, saying that rather than an app being central to the test and trace system, it was "the cherry on the cake".

Health Secretary Matt Hancock, however, said that with infection rates rising, every tool available must be used to prevent the spread of the disease, including the latest technology. "We have worked extensively with tech companies, international partners, and privacy and medical experts -and learned from the trials-to develop an app that is secure, simple to use and will help keep our country safe," he said.

The app uses Bluetooth signals to record when a user is in close contact with another user, generally meaning within two meters for 15 minutes or more. If someone tests positive for COVID-19, they can choose to share the result anonymously (匿名地）with their close contacts, who will each receive a warming and will have to isolate (隔离）for 14 days.

People aged over 16 will be encouraged to download the app by advertisements with the slogan:＂Protect your loved ones. Get the app."

Conservationists (野生动物保护者） have long known that using pandas, tigers and other charming species to promote their campaigns is a good way to raise money. But some people argue that focusing on these "flagship" animals can ignore equally threatened but less cute ones.

Now Jennifer McGowan at Macquarie University in Sydney and her colleagues suggest that we can have it both ways, after finding that funding for flagship species also helps other threatened species in the surrounding areas. McGowan's team first drew up a list of 534 flagship species in wildlife-rich hot spots around the world. The biodiversity areas were each split into grids (网格） of 100 by 100kilometer squares. The researchers then compared two conservation approaches across eight simulated scenarios (模拟场景） which assumed different levels of human activity and protected areas.

The first focused on protecting flagship species, while the second aimed to protect the maximum number of species in an area, regardless of their fundraising potential. Their study has found that targeting grid squares with flagship species also protected 79 to 89 per cent of the non-flagship species in that area. The figure rose to 97 per cent in some scenarios. "The findings could help when choosing which species to promote. Flagship species are very effective at getting the public to care, "she says.

Morgan Trimble, the author of a paper that has found scientists also have a preference for charming animals, says the results don't surprise her. "While I think it's important that we don't lose sight of the bigger picture --- conserving species is about conserving all the component parts of ecosystems, even the not-so-cute species ---I think highlighting flagship species in fundraising and education is a practical idea and appeals to human nature," she says. Trimble also asks what the alternative to using flagship species would be randomly picking species? McGowan's study found a random approach to choosing where to spend conservation funds only protected 39 to 55 per cent of the non-flagship species.

Many people believe sharks are dangerous and will always try to hurt or even kill humans.    11    

A shark exhibition at the National Aquarium in Baltimore, US, proves this. Visitors can touch young sharks, see their eggs develop and watch a dozen different species swim smoothly around a huge tank.

Most people fail to realize that shark attacks don't happen very often. Humans are more likely to be killed by lightning than by a shark.     12    . They can watch them develop inside the eggs and feel the skin of the older swimmers so as to learn, from an early age, not to fear sharks.

＂People fear what they don't know," said Nancy Hotchkiss, an organizer of the exhibition, which runs till December. "Sharks have been round for 400 million years and play an important role in the ocean's food chain. We want people to discover that sharks are amazing animals that need our respect and protection."

    13    .A study, published in January in the US magazine Science, found that almost all recorded shark species have fallen by half in the past eight to fifteen years.

Thousands of sharks are hunted in Asia for special foods, such as shark fin soup.     14    . More than half of all sharks caught are smaller than one meter long.

＂Some fishing methods are actually cleaning out the ocean," said Dave Schofield, the manager of the aquarium's ocean health program. "The fishermen threw them away like rubbish."    15    .