Junior school students in Harbin，Heilongjiang, had a "long weekend". They had four days off from Oct. 19-22. It was not for any festival, but was caused by serious smog.
    The smog was caused by high levels of PM 2.5 in the air.
    PM 2.5 is small particles（微粒） of pollution in the air with a diameter （直径） of 2.5 micrometers or less. Waste gas from cars and factories is the biggest cause of PM 2.5 pollution.  On Oct. 17, the World Health Organization named air pollution a cause of cancer.
    To better protect children, cities are taking action.
    On Oct. 21, Harbin Education Bureau decided to close primary and junior high schools for two days.
    Beijing started a program on Oct. 22 which has a warning system with four levels. The red warning is the highest warning level. It means that the next three days will see serious pollution.
    When a red warning is issued（发布）, schools will close.
    If there's pollution that's not as serious, the Beijing Commission of Education will ask schools to stop PE classes and outdoor activities.
How will students be informed?
    "First, the Commission of Education will inform schools online," Ye Yan, head of Beijing Shijingshanqu Experimental Primary School, told Beijing Times. "Then teachers will text students' parents."
    Will the days off affect the study plan?
    "Missing school days will be made up during the summer or winter vacations,"  said Wang Hao, a physical education teacher in Beijing Chaoyang district.
    For students in Harbin who had the long weekend, they would go to school on the next two Saturdays.

    Scientists have always believed that snails are not able to find their way home. But Briton Ruth Brooks, a retired teacher, has found that it is not true.

    Brooks began an experiment on snails after she got mad with the snails in her garden.

    The snails had eaten her vegetables. She didn't want to kill them, so she took them to another place. But she found they always seemed to come back.

    Brooks did an experiment. She marked the snails in her garden with nail polish(指甲油).

    She placed the snails in the area around her home and made notes of their movements.

    She found that snails have a strong homing instinct (本能); the longest returning snail traveled back 90 meters. Brooks has been named Britain's best amateur (业余的) scientist after her work won the BBC Radio 4 project, So You Want To Be A Scientist.

    She said, "I've always wanted to know whether the snails that eat my plants just come back when I move them, and if they do, what is their homing distance?

    "I would say on the evidence (证据) that it would be safe to take your snails away beyond 100m or even further. If you put them somewhere nice with some food, you can be almost certain that they won't come back."

    Have you got an eReader? Are you thinking of getting one? We asked some eReaders owners to give us their opinions.

    There are many things that people like about eReaders. "eReaders are really light, weighing less than most paperbacks," said Nathan Jones, a market researcher. "You can hold the book and turn the pages with one hand. An eReader is definitely more comfortable to read in bed or if you're lying on a sofa, plus mine's got a light so I can read in bed at night without disturbing my partner." Another big advantage is that you can store hundreds of books on them. "eReaders are perfect for travel," said Kiera Smith. "You can have lots of books in one device, instead of carrying loads of books in your luggage." The search functions are also popular. "You can look for a character by their name or for a place just by typing in the word. That's really useful," said Megan Malone, a sales executive.

    One user liked the function for increasing font size. "I've got poor eyesight," explained Harvey Callaghan, an engineer. "But the eReader is perfect for me as I can increase the font size." And Jennifer Saunders said, "I like eReaders because they're ecological. If we buy an ebook, we're helping to save trees as they don't use paper. Also, my eReader is solarpowered, so it only uses renewable energy." Best of all is the availability of hundreds of free books online. "Project Gutenberg has millions of titles and they're all free to download," said another user.

    One of the biggest complaints is that you can't find certain titles. "Many books are simply not available in electronic form," said Daisy Madison, an estate agent. If you want a specific book, one that is older, perhaps, or not a bestseller, it won't be available – at least, that was my experience."

    Others complained about the small delay in turning pages. "The gap between pressing the 'next page' button and the screen showing the page is really annoying," said Joel Bray, a shop assistant. "Also, you can't flick between pages so easily."

So, what do you think?

    Do you like pandas? Now you can watch them eat and play at iPanda. com 24 hours a day.

    The panda is a symbol of China. There are only about 1, 600 pandas in the wild(野外). You can also see them in the zoos of many countries like the US and the UK.

    Pandas have big black eyes and fat bodies(身体). When they eat, they sit on the ground and hold the food with two hands, just like children. They look very cute and funny.

    Pandas usually live for 30 years. Now many pandas in the wild have no food to eat. They are in danger and they need our help.