Experts generally consider BMI for kids to be a good measure of body fat, at least among heavier children. But in some cases it might be misleading. Athletic kids, in particular, may fall into the overweight category when they are actually muscular.

    Your child's BMI is important, but it is only a piece of the picture. If a BMI percentile (体重指数) indicates that your child is not within the healthy range, she needs a complete weight and lifestyle evaluation with a doctor.

    Experts recommend that kids of all ages and all weight categories follow these healthy guidelines to keep weight in control. It's easy to remember them as “5 — 2 — 1 — 0” every day.

    5 > Everyone in your family needs five servings of vegetables and fruit. Keep serving them even if kids don't eat them. If they see a food over and over, they're more likely to try it in the end.

    2 > Limit TV-watching to no more than 2 hours a day. Family members who use other “screens”—video games or computers, for instance, get less TV time. And kick the TV out of all bedrooms.

    1 > Get 1 hour of physical activity. Add up the minutes each family member is moving —it should be 60 minutes or more for each person. Start small and keep adding if necessary.

    0 > That's how many sugar-sweetened beverages you should have a day. Juice drinks such as lemonade and fruit punch, sodas, tea, and coffee can all have added sugar. Stick to water and reduced-fat milk instead.

    A 60-year-old homeless woman named Smokie has been sleeping outside in the dirt a few doors down from a man named Elvis Summers.

    Most mornings, she stops by Elvis's Los Angeles apartment and asks if he has any recyclable materials for her. Through these conversations, they struck up a friendship.

    One morning, Elvis saw a news article about man in Oakland who has been making tiny houses out of deserted materials. He was inspired to put off paying a few bills so he could buy the wood and hardware to make Smokie a brand new shelter. It took him five days to build it, and now, for the first time in ten years, Smokie has a place to hang the sign “Home Sweet Home”.

    “I had nowhere to really build it, so I just built it in the street outside of my apartment,” Elvis told Good News Network. “The local LAPD police have been super cool, and have told me they support it—as long as we move it to a different spot every 72 hours.”

    He made this pretty time-lapse(延时的) video showing how he did it. The materials, including two locks on the front door and strong wheels for moving it around, cost him about $500.

    “I've met so many homeless people, good people,” Elvis said in an email, “Since I built Smokie's , I've had several people asking me to make them a tiny home and it's turned into much more than just the one house I wanted to build.”

Although he runs an online retail store that sells EDM clothes, he has decided to launch an ambitious project to fund more shelters. He plants to get lighter and cheaper materials—without sacrificing the strength of the house—for the next round. Rick Sassen, a branch manager, kindly donated the roof shingles and cedar supporting Smokie's house, final items Elvis couldn't afford on his own. Sassen has promised to work out a deal on future building materials for the same cause.

    Most people who fly on passenger planes in the United States do not lose their luggage. Even if the luggage is lost, usually it is only delayed. Most "lost" luggage is found in a few days. Airlines search for the owners of unclaimed(未认领的) bags for up to three months. But when the owners cannot be found or the bags are not claimed, they are sold to a store in the small city of Scottsboro, in the southern state of Alabama.

    About one-half of one percent of all luggage passing through US airports is unclaimed. Many of the missing bags, and what is in them, are sold at the Unclaimed Baggage Center. Seven thousand items arrive at the store every day. Tom Barnes, who was shopping at the store said, "I can go into any of the large shopping centers, like the international malls. I can walk through there for an hour and come out with three items. But I come into this store, and then I come out with my car full of stuff."

    Brenda Cantrell, who works at the store, said, "The Unclaimed Baggage Center is the only store in America that buys and resells unclaimed baggage from the airline industry. You would be surprised at all the jackets, eyeglasses, neck pillows, blankets, laptops, Kindles, iPads, and you know, all kinds of expensive electronics."

    The store says it once sold a container for flowers for $80 that was found to be worth $18,000. And it says a painting it sold for $25 was later found to be worth $25,000.

    The store buys the luggage from the airlines. It does not examine the things inside them before buying them. Only about half of the items in the bags are suitable for sale at the store.

    Some people say it is not fair to the owners of the lost passage to sell their goods. Customer Daniel Martin is not one of them, saying, "I feel the airport may try to find the people that lose the things. If they've tried and they can't get a hold of them, it's better than throwing them away or just letting them rot in a warehouse somewhere."

    Unlike most other holidays, the history of April Fools' Day, sometimes called All Fools' Day, is not totally clear. The only point in time that can be agreed on as the beginning of this tradition was 1582, in France. Before that year, the New Year was celebrated for eight days, beginning on March 25th. The celebration reached the highest point on April 1st. With the reform of the calendar under Charles IX，the Gregorian calendar(公历，阳历) was introduced, and New Year's Day was moved to January 1st.

    However, because in those days communications were not as developed as they are today, many people did not receive the news for several years. Some people refused to accept the new calendar and continued to celebrate the New Year on April 1st. These backward people were considered "fools" by other people. They  were often sent on "fools" errands(徒劳无益的工作)  or were made the targets of jokes.

    This developed, over time, into a tradition of playing a trick on someone on the first day of April. The tradition eventually spread to England and Scotland in the eighteenth century. It was later introduced to the American colonies of both the Britain and France. April Fools' Day thus developed into an international fun feast, so to speak, with different nationalities specializing in their own kind of humor at the expense of their friends and families.

    When Gitanjali Rao shared how she likes "finding solutions to real problems”, it was hard to imagine this dynamic 11-year-old girl could settle a problem that has escaped scientists for years.

    In just three months, Rao came up with a device（装置）that can replace the costly and lengthy tests currently used to reliably determine lead levels in our fresh water. Inspired by the current litigation （诉讼）in Flint, Michigan, a case of water pollution from 2014 to 2015, Rao designed a new testing system that resulted in her being named America's Top Young Scientist for 2017.

    Rao had been following the water problem for about two years. She was amazed by the number of people affected by lead pollution in water and wanted to do something to change this. Gitanjali spent months trying to convince local high schools and colleges to give her lab time to continue her experiment. At home, Gitanjali worked on her project in the "science room” she asked her parents to create for her. Rao has created a device that uses three parts: a cartridge, a Bluetooth reader and an app. To put it simply, the cartridge contains carbon nanotubes（纳米管） that react to lead. This reaction is then registered by the Bluetooth reader, which sends a signal to a mobile app that can tell you immediately if your water is safe to drink.

    Rao appropriately named the device Tethys after the Greek goddess of fresh water, and is hoping to make a little improvement to get the device on the market. While we may not be aware of any lead pollution present in our aging pipelines, lead poisoning can cause delays in physical and mental development. With Rao believing that the "purpose of science is to make a difference”, her incredible invention could make a difference to millions of people in the United States.

    On a recent trip to London, I decided to visit some exciting new restaurants that are using technology to change the way people dine out. My first stop was at an Italian restaurant in the city center. When I walked into the restaurant, I was given a tray (托盘)and a special card, but I had no idea what to do next! The manager came up to me and explained that I could swipe (刷) my card at any of the food and drink stations in the restaurant, and that the card would record my order. No waiters necessary! I made my selection and then handed my card to the cashier. Once I'd paid for my meal, I collected it and made my way to the dining area on the second floor. The food was very delicious, but, I must admit, I didn't enjoy having to carry my food up two flights of stairs.

    On the next night, a friend of mine suggested that we visit his favorite high-tech restaurant. When we arrived, I was surprised to discover that there were no paper menus; instead, the menus appeared on the touch screen surface of the table. All we had to do was touch our choices with our fingers and wait for the waiters to bring us our meal. The touch screen tabletop also allowed us to change different tablecloths and even play games. We had so much fun playing games that we hardly touched our food when it arrived--we really should have told the waiter to give us takeaways instead.

    On my last day in London, I decided to get some tapas from a Spanish takeaway near my hotel. I had heard that the owners had placed a webcam (网络摄像机) at the restaurant to allow their customers to watch the long lunchtime queue (队列) online. This came in very handy for me. While I packed my baggage, I kept an eye on the queue and then raced to the restaurant when the lunchtime rush was over. Without that wonderful webcam, I could have missed my plane.