When the weather is hot, you go to a lake or an ocean. When you are near a lake or an Ocean, you feel cool. Why? The sun makes the earth hot, but it cannot make the water very hot. Although the air over the earth becomes hot, the air over the water is still cool. The hot air over the earth goes up. Then the cool air over the water moves in and takes the place of the hot air.

    Then you may ask, "Why is the ocean full of salt?" Scientists will say that the salt comes from the rocks. When the rocks get very hot or very cold, they crack (爆裂). Rain falls into the cracks. The rain then carries the salt into the earth and into the rivers. The rivers carry the salt into the ocean. And then you may doubt, "But the ocean does not get more salty every year. Scientists are not sure about the answer to this question.

    We know a lot about our world. But there are still many answers that we do not have, and we are curious about them.

    Imagine one day, the water taps in your house stop running. You have to buy water from shops. And still there {#blank#}1{#/blank#}water for everyone. Your mother has to save the family's shower water to do other things. Would you be able to stand that kind of life?

    Probably not. But that's what kids in Yemen are experiencing. Experts said Yemen is going to be the first country in the world to run out of water. {#blank#}2{#/blank#}a report, the capital, Sana'a, will run out of drinking water as early as 2025.

    Because of the shortage, the government often cuts the water supply. Hannan, an 18-year-old girl from Lahej, told the Times: "In a good week we'll have the water supply all week. But then the following week there will be water only for {#blank#}3{#/blank#}."

    Hannan said only rich people have enough water to use. They can buy water from the shops or from the water trucks. Private companies own the trucks. They {#blank#}4{#/blank#}every day to sell water—at very high prices. "A lot of people can't afford it," she said.

    The government is {#blank#}5{#/blank#}making use of seawater. But it will cost a lot and it may not happen soon enough to help the people of Yemen.

If you want to go shopping, think about how much money you can spend for new clothes.Think about the kind of clothes you really need.Then look for those clothes on sale.

There are labels (标签) inside all new clothes.The labels tell you how to take care of your clothes.The label for a shirt may tell you to wash it in warm water. A sweater label may tell you to wash it in cold water.The label on a coat may say "dry clean only". Washing with water may ruin (损坏) this coat. If you do as the directions on the label, you can keep your clothes looking their best.Many clothes today must be dry cleaned.Dry cleaning is expensive. When buying new clothes, check to see if they need to be dry cleaned.You will save money if you buy clothes that can be washed with water.

You can save money if you buy clothes that are well made.Well-made clothes last longer.They look good even after they have been washed many times. However, clothes that cost more money are not always better made.They do not always fit better.Sometimes less expensive clothes look and fit better than more expensive clothes.

Are you an "I" person or an "E" person? People have talked about it a lot online recently. They are part of a popular personality (性格) test called MBTI.

Everyone's result has four letters. "I" and "E" are the first letters. People are either "I", meaning introverted (内向的), or "E", for extroverted (外向的).

But sometimes introverted people can be outgoing, too. For example, an "I" person will hang out with a group of introverted friends. The person may do things a more "extroverted" person would do. For example, he or she may share their thoughts and feelings with others and ask strangers for directions.

I'm one of these kinds of people. Most of the time, I show an interest in new classmates and friends. I talk with them to show I'm friendly. But honestly, I like being alone and staying quiet.

I have to say, the personality test is just for fun. Everyone's personality is different. Don't let the test tell you who you are.

In this case, I was a bad example. I used to be very interested in my friends' MBTI results. I would get upset if their results didn't match the way I see them.

Soon, I think everyone might have a "personality stamp". For example, "P" people don't like to make plans. On the other hand, "J" people are planners and list-makers. My sister is a "P" person. She never plans. But one day, she was happily making a day-to-day travel plan for the holiday.

"I thought you were a 'P' person," I said to her.

"Do I have to follow what my personality test tells me?" she replied.

"Oh no," I said to myself. "I've taken the result too seriously."

The four letters don't tell you everything about a person. And no one should live according to what four letters tell you.

How can you learn about a city? City walks might be a great choice. Instead of simply {#blank#}1{#/blank#} around, city walkers follow some ways on different themes. Along the way, they enjoy the views, take photos, listen to the guide and take part in fun activities.

City walks are more and more {#blank#}2{#/blank#} in China. Not only travelers but also locals are becoming interested {#blank#}3{#/blank#} this. For travelers, it allows {#blank#}4{#/blank#} to deeply explore(探索) a city. For locals, it's a good chance to see something they haven't noticed before.

Zhang Xiaoxin,a college student, is a new comer to Changsha. By taking part in a city walk, she saw more closely {#blank#}5{#/blank#} the locals' daily lives were like. Unlike Zhang. Wang Yixuan {#blank#}6{#/blank#} up in Changsha. Thanks to city walks, she has visited places that she heard about before but {#blank#}7{#/blank#} set foot on. As the guide introduced the {#blank#}8{#/blank#} of these sites, she knew more about the city's past." Living here for over 20 years,I thought I was familiar with it enough,{#blank#}9{#/blank#} city walks let me see other sides of the city.

For many people, city walks are not just a way to travel but can be a part of their daily lives. Come on! Just start to observe (观察) everything around you whenever you walk, from your school or company to your home. You' ll always find {#blank#}10{#/blank#} surprising!

Hello, I am Jenny. I'm 13 years old. I live with my parents in a big city. I always study hard on weekdays. My grandparents live on a farm and I often visit them on weekends. On the farm are many kinds of animals, such as cows, sheep, pigs, dogs and chickens. I like to play with them because it can make me relaxed.

One day, I find a little duck on the farm. He has no family or friends, and he often walks alone. He is cute and I call him Tom. I decide to take care of him. After that, I often bring him some fresh fish and play with him. Little by little, the duck becomes friendly to me. Then, on Saturday mornings, when Tom sees me on the farm, he always runs up to me like a little dog. Sometimes he follows(跟着) me into the forest. We sit together and read books. We both feel relaxed. One Saturday evening, my grandfather asks me," Why does the little duck like you so much?"" Oh, because he can feel my love, grandpa."I answer happily.

Do you have an animal friend? If you don't, please try to get one!