After years of heated debate, gray wolves were reintroduced to Yellowstone National Park. Fourteen wolves were caught in Canada and transported to the park. By last year, the Yellowstone wolf population had grown to more than 170 wolves.

    Gray wolves once were seen here and there in the Yellowstone area and much of the continental United States, but they were gradually displaced by human development. By the 1920s, wolves had practically disappeared from the Yellowstone area. They went farther north into the deep forests of Canada, where there were fewer humans around.

    The disappearance of the wolves had many unexpected results. Deer and elk populations — major food sources (来源) for the wolf – grew rapidly. These animals consumed large amounts of vegetation (植被), which reduced plant diversity in the park. In the absence of wolves, coyote populations also grew quickly. The coyotes killed a large percentage of the park's red foxes, and completely drove away the park's beavers.

    As early as 1966, biologists asked the government to consider reintroducing wolves to Yellowstone Park. They hoped that wolves would be able to control the elk and coyote problems. Many farmers opposed the plan because they feared that wolves would kill their farm animals or pets.

    The government spent nearly 30 years coming up with a plan to reintroduce the wolvers. The U.S. Fish and Wildlife Service carefully monitors and manages the wolf packs in Yellowstone. Today, the debate continues over how well the gray wolf is fitting in at Yellowstone .Elk, deer, and coyote populations are down, while beavers and red fores have made a comeback. The Yellowstone wolf project has been a valuable experiment to help biologists decide whether to reintroduce wolves to other parts of the country as well.

    Your next Saturday night takeaway could be brought to you by a robot after a major food delivery company announced plans to use automated vehicles to transport meals. Europe's biggest online takeaway food company Just Eat has partnered with Starship Technologies to deliver food with robots on the streets of London later this month. “Nobody has ever done deliveries with land-based robots,” said Allan Martinson, the chief operating officer of Starship.

    The robot courier can travel up to 4 miles per hour for about 10 miles. It uses a GPS signal and nine cameras to navigate (确定方向). Instead of a person arriving at their door, customers could find themselves receiving a notification (通知) on their phone that says a robot is on its way and a code to unlock the automated courier. “Put the code in, the robot opens up, and there's your food,” said David Buttress, chief manager of Just Eat.

    The robot, which has so far been tested in Greenwich, Milton Keynes and Glastonbury, costs ￡1 to transport within 3 miles, compared with the ￡3 to ￡6 it costs for a human courier. To date 30 robots have driven nearly 5,000 miles without getting into an accident or finding themselves picked on by passers-by. They have driven in more than 40 cities around the world, including London and Tallinn, Estonia.

    An initial worry was how the public would react to robots. But Martinson said the public has been calm when passing the delivery machine on the streets. “The most surprising reaction has been the lack of reaction,” said Martinson.

    Another significant fear was that people would disrupt (扰乱) the robots, or try to steal them and their contents. To prevent this, the robot is fitted with nine cameras, two way audio, and movement sensors that send a warning if it is lifted off the ground. And it opens only with a pass code provided to the customer via a notification. “It's much easier to shoplift than it is to steal a robot,” said Martinson.

    My wife and I went to this vegan(严格的素食主义的)restaurant to give it a try.As we were eating our pepper and salt tofu, a young lady named Debra walked in. She wasn't aware that the place is vegan and was looking for some meat. My wife and I talked up the place and invited her over to try some of our tofu. Debra tried it, nodded and went out.

    After a few minutes, she and her mother both walked back in. We were having the rest of our meal at that time, so we told her what we had ordered. Debra then asked the waitress to just repeat our order for them. Next, Debra said, "And we want to pay for their meal", pointing to my wife and me. We tried to say no, but Debra wouldn't listen.

    That was not the end of it. Hugs were in order. Debra came over to our table and my wife got up to hug her. Debra hugged my wife and put $100 into her hand. My wife firmly said NO, but Debra insisted. Debra kept talking about our kindness, and we did the same about hers and her mother's. With tears in the eyes, the workers were blown away by this whole exchange between four strangers. I left the waiters a tip that would cover all of our meals and we were on our way.

    I've been witnessing so much kindness, especially over the last few years, as I began to pay more attention. We now have a new favorite restaurant and every time we go there my plan is to pay for someone else's meal.

    It all started in 2007 when James Bowen, a thirty­something drug addict who survived by playing guitar on the street, found an orange cat sitting in front of the door of his apartment.

    Bowen noticed the cat was wounded. Without hesitation, the young man took him to the Humane Society and spent the little money he had on medicine to heal him.

    Shortly thereafter, the cat, who was healing and feeling much better, began to follow the musician when he left the house. Then one day the cat got on the bus that Bowen took to the place where he worked.

    That's how the cat, who had recently been named Bob, began to accompany his human friend to his musical performances. Bob's mere presence attracted the attention of passers­by. He and Bowen would finish off each song with a high five. Pretty soon, the images of Bob wearing a scarf while sitting on the musician's shoulder, or keeping him company while he played the guitar, began to go viral all over the world.

    Eventually, the news found out about the pair and did a story for the magazine Islington Tribune. It was not long after that when a book agent appeared in their lives and gave them a chance to tell their story.

    By then, Bowen, who had managed to get away from drugs, wrote a novel called A Street Cat Named Bob. He related in great detail how meeting the cat changed him.

    The book soon sold more than six million copies and even spread beyond the borders of the United Kingdom. In fact, it was translated into thirty languages.

    Through all of these changing circumstances, Bob has always been with Bowen—on his shoulder.

    You can't make up a story like this. But life always gives opportunities to those who know how to get hold of them. So if you are ever in a position where a cat has chosen you, don't ignore it. You can't imagine all the good that life may have in store if you decide to accept the proposal.

That morning in September, at a five-kilometer race, I waited for my 11-year-old son at the finish line. He'd run 30:34 at another 5k in late spring, so I 1 he could run a 5k in about 30 minutes. When I didn't see him at the 35-minute mark, I began to 2 .

It'd already been an 3 morning. About an hour earlier, when we drove into town, my son noticed a lovely tiny green tree cricket （树蟋） in my car. It jumped onto my son's hand where it stayed so long that we eventually gave it a name: Little Friend.

Minutes before the race, it jumped onto the sidewalk. Maybe it wanted to seek freedom, but this wasn't a safe place due to the 4 pedestrian traffic. So my son knelt and 5 his hand. Little Friend came back. But I told him he would 6 it during the race.

I ran well and felt thrilled at the finish line. However, that 7 gave way to anxiety when my son didn't show up. I 8 asking people if they'd seen him. No one had. So I returned to the race headquarters. In my confusion, I didn't even see him 9 the finish line. But there he was, just ahead of the 45-minute mark, with Little Friend 10 on his right thumb.

My 11 were wrong. My son didn't run fast, and he didn't lose Little Friend. These two 12 seemed somehow related. He 13 a cold he was getting over, but I knew it was more than that.

Sometimes life gives you something beautiful, but fragile （易碎的）. There's no need to 14 ahead. Treat it 15 and hold on when you can.

Quantum mechanics (量子力学) is a branch of science that studies the smallest particles (粒子) in the universe, like atoms (原子) and even smaller things. It might sound super complex, but let's break it down in simple language.

Imagine you have a small particle, like an atom. In the world of quantum mechanics, these particles don't behave like the things we see in our everyday lives, like balls or cars. Instead, they act kind of like waves and particles at the same time, which is really strange!

One of the most famous ideas in quantum mechanics is the "Uncertainty Principle", raised by physicist Wemer Heisenberg. This principle says that we can't precisely know both the position and the speed of particle at the same time. It's not because our measuring tools are bad; it's because the particles themselves are naturally uncertain.

Another weird thing about quantum mechanics is something called "Entanglement". Imagine you have two particles that are connected in a special way. If you change one of them, the other instantly changes, no matter how far apart they are. It's like they're talking to each other faster than the speed of light, which goes against what we know from everyday experiences.

Quantum mechanics also deals with probabilities. Instead of saying, "This particle will be here at this exact time," scientists say, "There's a certain chance it'll be here, and a certain chance it won't." It's like predicting the weather, but on a super small scale.

In a nutshell, quantum mechanics is a strange and fascinating world where particles act both like waves and particles, where you can't know everything about a particle at once, and where particles can be mysteriously connected no matter how far apart they are. It's a mind-boggling field that challenges our understanding of how the universe works, and even though it's tough to grasp, it's an essential part of modern physics.