Probably no other musical instrument is as popular as the guitar around the world. Musicians use the guitar for almost all kinds of music. Country and western music would not be the same without a guitar. The traditional Spanish folk music called Flamenco could not exist without a guitar. The sound of American blues music would not be the same without the sad cry of the guitar. And rock and roll music would almost be impossible without this instrument.

    Music experts do not agree about where the guitar was first played. Most agree it is ancient. Some experts say an instrument very much like a guitar was played in Egypt more than 1,000 years ago. Most experts say that the ancestor of the modern guitar was brought to Spain from Persia sometime in the 12^th century. The guitar continued to develop in Spain. In the 1700s it became similar to the instrument we know today.

    Many famous musicians played the instrument. The famous Italian violins Niccole Paganism played and wrote music for the guitar in the early 1800s. Franz Schubert used the guitar to write some of his famous works. In modern times Spanish guitarist Andres Segovia helped make the instrument extremely popular.

    In the 1930s, Les Paul began experimenting to make an electric guitar. He invented the solid-bodied electric guitar in 1946. The Gibson Guitar Company began producing its famous Les Paul Guitar in 1952. It became a powerful influence on popular music. The instrument has the same shape and the same six strings (弦) as the traditional guitar, but it sounds very different. Les Paul produced a series of extremely popular recordings that introduced the public to this music. Listen to this Les Paul recording. It was the fifth most popular song in the United States in 1952. It is called “Meet Mister Callaghan.”

    Along the river banks of the Amazon and the Orinoco there lives a bird that swims before it can fly,flies like a fat chicken,eats green leaves,has the stomach of a cow and has claws（爪）on its wings when young.They build their homes about 4.6m above the river,an important feature（特征）for the safety of the young.It is called the hoatzin.

    In appearance,the birds of both sexes look very much alike with brown on the back and cream and red on the underside.The head is small,with a large set of feathers on the top,bright red eyes,and blue skin.Its nearest relatives are the common birds,cuckoos.Its most striking feature,though,is only found in the young.

    Baby hoatzins have a claw on the leading edge of each wing and another at the end of each wing tip.Using these four claws,together with the beak（喙）,they can climb about in the bushes,looking very much like primitive birds must have done.When the young hoatzins have learned to fly,they lose their claws.

    During the drier months between December and March,hoatzins fly about the forest in groups of 20 to 30 birds, but in April,when the rainy season begins,they collect together in smaller living units of two to seven birds for producing purposes.

    Starting the day on an egg could keep your blood pressure under control, research suggests. Scientists have shown that eggs produce proteins with a function similar to that of powerful blood pressure-lowering drugs.

    The research, from the University of Alberta in Canada, showed that when eggs come in contact with stomach enzymes (酶) they produce a protein that acts in the same way as Ace inhibitors, but more work is needed to show the effects outside a lab and in the human body.

    Earlier this month, British researchers declared that, contrary to popular beliefs, it is healthy to go to work on an egg. They concluded that the type of cholesterol (胆固醇) found in eggs has little effect on increasing heart disease risks.

    Researcher Professor Bruce Griffin, from the University of Surrey, said, "The wrong beliefs linking egg eating to high blood cholesterol and heart disease must be corrected. The amount of fat in our diet has an effect on blood cholesterol that is several times greater than the relatively small amounts of cholesterol found in eggs. The UK public do not need to be limiting the number of eggs they eat. They can be encouraged to include them in a healthy diet as they are one of nature's most nutritious foods."

    The British Heart Foundation dropped its three-egg-a-week limit in 2005. However, almost half of Britons believe the limit still applies.

    Many leading AI researchers think that in a matter of decades, artificial intelligence will be able to do not merely some of our jobs, but all of our jobs, forever transforming life on Earth.

    The reason why many reject this as science fiction is that we've traditionally thought of intelligence as something mysterious that can only exist in biological organisms, especially humans. But such an idea is unscientific.

    From my point of view as a physicist and AI researcher, intelligence is simply a certain kind of information-processing performed by elementary particles(基本粒子) moving around, and there is no law of physics that says one can't build machines more intelligent than us in all ways. This suggests that we've only seen the tip of the intelligence iceberg and that there is an amazing potential to unlock the full intelligence that is potential in nature and use it to help humanity.

    If we get it right, the upside is huge. Since everything we love about civilization is the product of intelligence, amplifying(扩大) our own intelligence with AI has the potential to solve tomorrow's toughest problems. For example, why risk our loved ones dying in traffic accidents that self-driving cars could prevent or dying of cancers that AI might help us find cures for? Why not increase productivity through automation and use AI to accelerate our research and development of affordable sustainable(可持续的) energy?

    I'm optimistic that we can develop rapidly with advanced AI as long as we win the race between the growing power of our technology and the knowledge with which we manage it. But this requires giving up our outdated concept of learning from mistakes. That helped us win the race with less powerful technology: We messed up with fire and then invented fire extinguishers, and we messed up with cars and then invented seat belts. However, it's an awful idea for more powerful technologies, such as nuclear weapons or superintelligent AI—where even a single mistake is unacceptable and we need to get things right the first time.

    When I was growing up, Mother's Day was as important as Christmas.

    The energy around the house was always positive（积极的）, mostly thanks to my father who made sure that his kids appreciated their mother, We would clean the house, and Mum got breakfast in bed in the morning and didn't have to lift a finger all day. And in the evening, we went to a restaurant for a traditional Mother's Day dinner.

    What I learned from my father over the years, was that no matter what, he always put my mother before himself. He absolutely loved her and never let her forget that. And from my parents, I learned a thing or two about how to love.

    I maintain（保持） my father's Mother's Day tradition with my wife. Growing up, I learned that showing affection to the woman you love or who gave birth to you is an important part of life. You see, it goes both ways, and the love you have for your mother comes back to you again and again.

    Believing that and feeling it when you can may keep you from being lonely, even if your mum isn't close by or has passed away. There are a number of us who no longer have a mother in our lives, and truth be told, there are often times when I wish my mum were still here to comfort me. So instead, I remember the times she did just that. It makes me smile, and somehow, those memories of a more simple and loving life give me the comfort I'm looking for.

    My wife's mother is still around, however, and it's great to have that "mother energy" in my life still. Having this relationship with my mother-in-law is nice because it gives me someone to be there for on Mother's Day, and any other day of the year.

    If you are mum-less, you too should find a deserving woman in your life and celebrate Mother's Day with her. If you don't know anyone, there are plenty of lonely mums in rest homes who would enjoy your company for a couple of hours. The visit will make both of your days, and perhaps your lives, a little bit better.

Recess (课间休息) time has been dropping for many children in America. This drop began the same year the No Child Left Behind Act (NCLB) was passed. The law aimed to make American education system more internationally competitive by introducing achievement goals for schools. And the goals are gauged (评定) by standardized tests in reading and math. If schools missed their achievement goals, they could be in trouble, including loss of funding.

It's no surprise that teachers have felt the pressure to make sure students perform well on standardized tests. When educators are facing pay cuts, loss of funding to their school and perhaps even the loss of their jobs, it's no wonder that they started questioning if recess was a waste of time. This pressure to bring even more learning into the school day is especially felt by underperforming, low-income schools that are already short of funding.

It may seem strange to send kids out to play when they're falling below state standards, but getting outside for unstructured (散乱的) play may be more helpful than keeping kids in the classroom all day.

"Moving, running and playing outdoors freely have great influence on children. These activities play a role in children's abilities to focus and control themselves throughout the day," Marie Conti says, a famous educator of early childhood education. The mind cannot be educated without using the body. Learning is a whole of thinking and moving," she added.

Recess time makes it possible for children to learn something they can't get in class. Asking other kids to play, explaining the rules of a complex game and ending arguments are all important life lessons that children can only learn if they're given time to play. When something unhappy happens, children can find a way to get back to having fun themselves.

The physical activities kids take part in during recess can also reduce stress levels and allow children to feel more relaxed. In an education system that. Continues to place higher expectations on children to perform to a certain standard, less stress is just what the doctor ordered.