One day, I took an underground to work, I saw something that made me very sad. On the tube (underground in London), a mother kept looking at her phone screen and playing a game with her daughter sitting beside her. The little girl, about 5 years old, was talking to her mother about herday, repeating the next stop's name cheerfully, praising her mother's long nails—trying to draw her mother's attention. Her mother just nodded and mumbled "Mm, hm" with her eyes glued to the screen, busy passing the levels of the game. I watched the girl give a final try to at least get her mum to look at her, but it was no use. Then the little girl turned silent. It was a shame the mother didn't notice that.

    It broke my heart and got me wondering—what kind of game would make the mother forget she has the most beautiful thing in the world, the human she created, the person she loves with all her heart? What it meant when she couldn't look into her daughter's eyes and even stop to listen to the girl?

    Some parents are almost like the teenagers, always on their phones with mindless games or going through Facebook. Perhaps parents have many things to deal with, but sometimes they are everything to their kids.

    This is not an isolated example. I've seen too many such examples. I might not be a parent myself, and probably still have a long way before becoming one, but I know what I saw isn't right.

    The scene used to be seen among teenagers very often when parents complained how their children were crazy about their mobile phones. Look how the situation has changed! The parents have become "technology slaves", that is to say, they can't control themselves while using mobile phones.  Now some middle-aged parents hold the best iPhones or Samsung phones, which are probably the only two brands they know. They are playing the simple games with so expensive mobile phones. I'm uncertain whether to laugh or to cry. But my hope is that this storm passes.

已知实数a，b满足ab=3，a﹣b=2，则a²b﹣ab²的值是____．

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    To control the nation's growing problem with food wastage, the South Korean government has started a special initiative (倡议) ---“Pay as You Trash”. According to the initiative, the South Korean government has three methods in place to charge citizens for the food thrown away. One is through an RFID (Radio Frequency Identification) card — when users tap this card over a specially designed food waste bin, the lid will open. This waste is automatically weighed and recorded in the user's account. The user needs to settle this bill every month.

    The second billing method is through pre-paid garbage bags. These specially designed bags are priced based on the amount of space. For instance, in Seoul, a 10-liter garbage bag costs around 190 won (less than $1). There's also a bar code management system in place, in which residents (居民) throw food waste directly into dustbins and pay for it by buying bar code stickers attached to the bin.

    Even before the pay-by-weight system was introduced, South Koreans were still being charged for food waste — the cost was simply divided equally among the residents of each apartment block. The new system is not only fair, but is also designed to make consumers really feel the pinch of too much waste. The more food they throw out, the more they end up paying.

    Thanks to the initiative, residents like Seoul housewife Ms. Kwan are now adopting creative methods to avoid food waste. She makes sure to pour all the liquid out of leftover food before throwing it away. While preparing vegetables, she tries to use as much as the eatable parts as possible in order to reduce waste.