How does a young dog or cat get to know a new home? The animal uses its nose. Right away it smells its new places. Then it makes wider and wider circles, smelling all the time. Before long it can find its way home very well, even in the dark. It simply follows something it knows well.

    Stories happen about animals who found their way across land they had never smelled before. Take the case of Smoky, a small white cat. Smoky had some funny red hair around its right ear. One day Smoky and his owner began a long journey. They were moving from Oklahoma to Tennessee. When they were just eighteen miles from their Oklahoma home, Smoky jumped out of the car. Then he found his way back to the old house. There he wandered around outside for many days. Finally he disappeared.

    A year later Smoky meowed at the door of a house in Tennessee. A man opened the door. "Is that you, Smoky?" he said in surprise. At first he couldn't believe it. Then he saw the red hair around its right ear. It was Smoky!

    I am an apple. I'm a kind of sweet1You can find me grow in many places of the world, but I can't grow well in very hot places2 very cold places.

    I am not like my cousins 3and bananas. I am rounder than a pear and bananas are4than me. I am delicious,5people all over the world like to eat me. They can usually eat me6washing me. They can also cook me to 7all kinds of food, sometimes they put me in cans（罐头）to send me to other places of the world. Almost everyone can have 8 to buy me because I'm so cheap.

    I can also help people get9 There is a saying10English: An apple a day keeps the doctor away. Don't you think that I'm very great? I have many vitamins（维生素）inside, they are 11for you. I really wish to make you happy and healthy. so don't forget to 12me as often as possible（尽可能经常地）.

    But I also need your13, if you want to make me taste better, you must14 me well. Thank you for your love. I'll try to grow well and15sweeter. Then you will like to eat me a lot more.

    Most people agree that trees look nice, but not everyone knows that trees can also help cities save money. A few years ago, the US Forest Service studied trees in Chicago. They found that just one tree can save a city hundreds of dollars over its lifetime.

    Trees can save money by helping people save energy(能源). Trees stop the sun shining on buildings. They also block(挡住) the winter wind. That helps people use less energy to make their homes or offices warm or cool. Saving energy is saving money.

    Trees have another way to help a city save money. When it rains, there will be a lot of water in a city's sewers (下水道). Cities need lots of money to clean that water. But before the rainwater gets to the dirty sewers, trees can take some into themselves. With the help of trees, there is less water to clean.

    Climbing Mount Qomolangma, the World's highest mountain, has now become more difficult. The government of Nepal asks climbers to come down the mountain with at least 18 pounds of garbage. That's the average amount of garbage a climber leaves behind on Mount Qomolangma.

    Climbers would leave garbage along the way. This helps climbers keep their bags light, so they would have energy to reach the summit.  The garbage problem in Mount Qomolangma is not new. In 2013, climbers carried down a total of four tons of garbage.

    The new rule came into effect in April of 2014. To make sure it is followed, climbers will have to hand in some money to the officials before they climb the mountain. When they climb back down the mountain, the officials will check them to make sure they bring down the 18 pounds of garbage. If they do, their money will be given back to them.  If not, climbers won't get their money back. Also, the officials won't let these people climb the mountain again.

    "What? You too? I thought I was the only one." Have you ever said to someone? If so, you may have ended up becoming friends.

    It seems that similarity often helps form a friendship. Aristotle once said, "Some define (给……下定义) it (friendship) as a matter of similarity; they say that we love those who are like ourselves."

    Now, there are some scientific explanations for this idea. The scientists from the University of California said friends have similar brains, Scientific American reported.

    The scientists invited 42 university students to take part in a scientific test. Each student watched the same set of videos. At the same time, the scientists scanned (扫描) their brains and recorded their brain activities.

    According to their study, friends who watched the same videos reacted (反应) in similar ways. Similar parts of their brains lit up while watching the videos, especially the parts that were connected with motivation, learning and memory. However, people who weren't friends had different reactions to the same videos.

    "Having close friends whose brains react like ours may be rewarding because it reinforces (加强) one's own values, opinions and interests," lead scientist Carolyn Parkinson told Business Insider.

    But brain similarity is not the only thing that can result in a friendship. Scientists from the University of Leipzig, Germany, found that a friendship is also based on how physically close you are to someone. They did a scientific test on first-year college students who met in class for the first time. In this test, students who sat next to each other were more likely to become friends.