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.

    Miss Parker taught physics in a New York school. Last month she explained to one of her classes about sound ,and she decided to test them to see how successful she had been in her explanation. She said to them, “Now I have a brother in Los Angeles. If I was calling him on the phone and at the same time you were 75 feet away, listening to me from across the street, which of you would hear what I said earlier, my brother or you and for what reason?”

    Tom at once answered, “Your brother. Because electricity travels faster than sound waves.”“That's every good,” Miss Parker answered; but then one of the girls raised her hand, and Miss Parker said.“Yes, Kate.”

    “I disagree,” Kate said.“Your brother would hear you earlier because when it's 11 o'clock here it's only 8 o'clock in Los Angeles.”

    A black hole is created when a large star burns out. Like our sun, stars are unbelievably hot furnaces(熔炉) that burn their own matter as fuel. When most of the fuel is used up, the star begins to die.

    The death of a star is not a quiet event. First there is a huge explosion. As its outer layer is blasted off into space, the dying star shines as brightly as a billion suns.

    After the explosion, gravity pulls in what's left of the star. As the outside of the star sinks toward the center, the star gets smaller and smaller. The material the star is made of becomes tightly packed together. A star is so solid that a teaspoon of matter from it weighs billions of pounds.

    The more the star shrinks(收缩), the stronger the gravity inside it becomes. Soon the star is very tiny, and the gravity pulling it in is unbelievably strong. In fact, the gravity is so strong that it even pulls light into the star! Since all the light is pulled in, none can go out. The star becomes black when there is no light. Then a black hole is born!

    That's what we know about black holes. What we don't know is this: What happens inside a black hole after the star has been squeezed into a tiny ball? Does it keep getting smaller and smaller forever? Such a possibility is hard to imagine.

    But if the black hole doesn't keep shrinking, what happens to it? Some scientists think black holes are like doorways to another world. They say that as the star disappears from our universe, it goes into another universe. In other words a black hole in our universe could turn into a "white hole" in a different universe. As the black hole swallows(吞噬) light, the white hole shines brightly--somewhere else. But where? A different place, perhaps, or a different time--many years in the past or future.

    Could you travel through a black hole? Right now, no. Nothing we know of could go into a black hole without being crushed(挤压). So far the time being, black hole must remain a mystery.

Black holes are a mystery--but that hasn't stopped scientists from dreaming about them. One scientist suggested that in the future we might make use of the power of black holes. They would supply all of Earth's energy needs, with plenty to spare. Another scientist wondered if a black hole could some day be used to swallow earthly waste--a sort of huge waste disposal(处理) in the sky!

    Lost iPhone

    Unexpectedly, I lost my white iPhon5s in Midtown on Friday night. It had a blue green cover on it. There are many pictures of my son on it, and I'm heartbroken， Please return, no questions asked. Reward. Reply to: -2652255359@craigslist.org

    Do you need a babysitter that you can trust?

    My name is Tina. I am a responsible babysitter that you can trust. If you are looking for someone dependable and affordable I am that person! I HAVE MORE THAN 30 YEARS OF EXPERIENCE (including disabled children)! I am a retired Home Health Aid and absolutely love children. I work with my sister Iris who has also 20+years as a teacher's assistant. WE LOOK FORWARD TO MEETINC YOU! Available 24 hours and flexible with fees! I am fully bilingual—Spanish/English. Please email me or call 712-867-7688.

    I BABYSIT ONLY AT MY HOME.

    I accept children from all ages. Fee starts from $100-$150 a week depending on the hours. I am very flexible and my fee can change. Feel free to contact me via email or on my cell phone 566-67-1873 and we can work something out.

    Part-time Chinese Babysitter Wanted

    Part-time Chinese speaking babysitter needed to assist with one-year-old twins and to perform some light house work as needed. Assistance needed Fridays and occasional weekends. Please provide your salary expectation. College students are welcome to apply.

    Reply to: comm-encbq-2652113885 @craigslist.org

    If you don't have a college degree, you're at greater risk of developing memory problems or even Alzheimer's (老年痴呆). Education plays a key role in lifelong memory performance and risk for mental disorder, and it's well documented that those with a college degree possess a cognitive（认知的） advantage over their less educated counterparts in middle and old age.

    Now, a large national study from Brandeis University published in the American Journal of Geriatric Psychiatry shows that those with less schooling can significantly make up for poorer education by frequently engaging in mental exercises such as word games, puzzles, reading, and lectures.

    “The lifelong benefits of higher education for memory in later life are quite impressive, but we do not clearly understand how and why these effects last so long,” said lead author Margie Lachman, a psychologist. She suggested that higher education may encourage lifelong interest in cognitive efforts, while those with less education may not engage as frequently in mental exercises that help keep the memory agile (敏捷地).

    But education early in adulthood does not appear to be the only route to maintain your memory. The study found that intellectual activities undertaken regularly made a difference. “Among individuals with low education, those who are engaged in reading, writing, attending lectures, doing word games or puzzles once a week or more had memory scores similar to people with more education,” said Lachman.

The study, called Midlife in the United States, assessed 3,343 men and women between the ages of 32 and 84 with a mean age of 56 years. Almost 40 percent of the participants had at least a 4-year college degree. The researchers evaluated how the participants performed in two cognitive areas, verbal memory and executive function — brain processes involved in planning, abstract thinking and cognitive flexibility. Participants were given a battery of tests, including tests of verbal fluency, word recall, and backward counting.

    As expected, those with higher education said they engaged in cognitive activities more often and also did better on the memory tests, but some with lower education also did well, explained Lachman.

    “The findings are promising because they suggest there may be ways to level the playing field for those with lower educational achievement, and protect those at greatest risk for memory declines,” said Lachman. “Although we can not rule out the possibility that those who have better memories are the ones who take on more activities, the evidence is consistent with cognitive plasticity (可塑性), and suggests some degree of personal control over cognitive functioning in adulthood by adopting an intellectually active lifestyle.”

As online learning becomes more common and a mass of resources are changed to digital form, some people have suggested that public libraries should be shut down and everyone should be given an iPad with an e-reader subscription (订阅). They believe that it will save local cities and towns money, provide more materials and encourage more people to read.

 However, it would be a serious mistake to replace libraries with tablets (平板电脑). First, digital books and resources are related to less learning and more problems than print resources. A study found that people read 20-30% slower on tablets, keep 20% less information, and understand 10% less of what they read. Additionally, staring too long at a screen has been shown to cause more health problems than reading print does. 

Second, it is incredibly narrow-minded to believe that the only service libraries offer is book lending. Libraries have lots of benefits, and many are only available if the library has a physical location. Some of these benefits include acting as a quiet study space, giving people a way to communicate with their neighbors, holding classes on a variety of topics, providing jobs, answering visitor questions, and keeping the community connected. One neighborhood found that, over a third of residents reported feeling more connected to their community after a series of local library instituted community events. Similarly, a survey conducted in 2015 found that nearly two-thirds of American adults feel that closing their local library would have a major effect on their community.

While replacing libraries with tablets may seem like a simple solution, it would encourage people to spend even more time looking at digital screens and end access to many of the benefits of libraries. In many areas, libraries are such an important part of the community network that they could never be replaced by a simple object.