In this task, you're given an article and an answer. Your task is to generate the question for the answer based on the given article.

[Q]: Article: Polar bears are born in dens on land and their mother stays with them for the whole winter without eating anything. The mother and the babies come out from the dens around March, _ from a long winter and must immediately go hunting to find food to stay alive. Now, the only hunting they know is to catch seals from floating ice in the open ocean. In March, polar bear mothers and babies have to swim from the land in Spitsbergen to the edge of the polar ice cap. Normally this is a short swim, since in March the polar ice cap is very close to the land, and the polar bears, and even the babies, are good swimmers. However, last year we saw that the polar ice cap had become smaller in size due to global warming. Swimming hundreds of miles, especially when they are hungry and have babies following them, is really hard, and many bears are dying because of starvation. The polar bear population in the Spitsbergen area was once threatened by hunters. In the 1970s, a ban on hunting was imposed and the polar bear population has been steadily increasing from just a few hundred to about 2,000 to 3,000. This was a great success story. However, now, because of global warming, the population is again in danger. If we do not stop making so much carbon dioxide, we will lose these beautiful animals forever. The polar bears are just one example of animals that have become endangered because of man's appetite for energy obtained by burning fossil fuels. All life on earth could be in danger unless we change our ways. What can we do? To reduce the amount of carbon dioxide in the air we must save and make energy without burning coal and oil. Instead, we can use the sun or the wind to generate electricity. We must also cut down on needless driving and turn off things that use electricity when we are not using them. In addition, we have to stop cutting down forests and start planting more trees.
Answer: To catch seals for food.
[A]: Why do the bears swim to the edge of the polar ice cap?

[Q]: Article: Mass media are tools of communication. They allow us to record and pass information rapidly to a large, scattered audience. They extend our ability to each other by helping us overcome limits caused by time and space. Mass media can be divided into two groups: print media and electronic media. By print media, we mean books, newspapers and magazines. Electronic media include television, radio and movie. There are a number of ways in which mass media make daily life easier for us. First, they inform and help us keep a watch on our world. They gather and pass on information we would be unlikely or unable to gain on our own. Second, mass media help us to arrange our time and life. What we talk about and what we think about are greatly influenced by the media. When people get together, they tend to talk about certain happenings on the newspapers or on TV. Because we are provided with differing points of view through different kinds of media every day, we are able to comment on all sides of a certain issue. Third, mass media help us to connect with various groups in society. Through mass media, we are able to keep in contact with politicians in the world; with famous actors and actresses, and with our beloved singers. Fourth, the media help to socialize us. We learn about the preferred behavior and values from the people we meet as well as from the media. Through portrayals of people, the media tell us what proper behaviors are. By doing so, they teach us standards of behavior and values, and help us in our daily life. Fifth, the media are used to persuade people. A good example is advertisements through the media. Newspapers, magazines and TV are filled with all kinds of colorful, persuasive advertisements. Though many advertisements may not say openly that they want you to buy a certain product, they describe their products in such a way that you may want to but them. Sixth, the media entertain. All of the media make some effort trying to entertain their audience. For example, even though the newspaper is a main medium of information, it also contains entertainment features. Many newspapers offer their readers at least some of the following: comics, fiction books and puzzle games, televisions and magazines are devoted mainly to entertainment. It is guessed that in the future, the entertainment function of mass media will become even more important than it is now.
Answer: Mass media help us spend time with others in a friendly way.
[A]: According to the passage, which of the following statements isn't true about medium?

[Q]: Article: How did the ancient Chinese keep food warm in winter? Facilities like electric rice cookers, microwaves, and electric kettles, make it easy for people to keep food warm and enjoy a comfortable winter. So how did Chinese people in ancient times keep food warm in winter without these? In fact, ancient Chinese people used their own methods of heat preservation as early as the Shang and Zhou dynasties. * "Wen Ding", ancient rice cooker One of the major functions of an electric rice cooker is to keep food warm. The "Wen Ding", an ancient cooking container, served the same purpose, but instead of using electric energy, the ancient cooking container, served the same purpose, but instead of using electric energy, the ancient cooking container preserved heart by burning fuels like charcoal. The "Wen Ding" unearthed in Nanjing in 1989 is thought to be the oldest of its kind discovered in China, dating back to the Stone Age, The craftsmanship of making the "Wen Ding" was developed in the Bronze Age. The bronze Ding from Shang and Zhou dynasties took on different shapes and structures. * "Ran LU", ancient small hot pot The "Ran LU" is a small size cooking vessel made of bronze, which can be divided into three parts. A charcoal stove forms the main structure, with a bottom tray to hold charcoal ashes, and a movable cup at the top. Some experts have concluded that the vessel's structure suggests it may have been used as a small hot pot and that these vessels became popular in the Warring States Period(475--221 BC) *Bronze You, ancient kettle The Bronze You was one of the most common wine containers during the Shang and Zhou dynasties. The Bronze You can also be used to warm wine. For example, the Bronze You with beast mask design, unearthed in Jiangxi province, has an opening where charcoals could be placed. Just as people today can't do without an electric kettle, the Bronze You allowed people to enjoy a hot drink. *Bronze Yan, ancient steamer Although the "Wen Ding" was effective at keeping food warm, the ancient Chinese people later found that its burning produced pollution. As a result, the Bronze Yan was made with a two-tier structure and used to steam rice and other grains. After the Eastern Han Dynasty (AD 25-AD 220), further improvements to the Bronze Yan led to the modern-day steamer.
Answer: In the Warring States Period.
[A]:
When did the "Ran LU" become popular?