What is the sky? How high is it? What color is it? What birds can live above it? These questions are difficult to answer, aren't they? In fact, the sky has no color. Then why does the sky look blue?

    We know that there is air around the world. When planes fly, they need air to lift their wings. Planes can't fly very high. That is because the air gets thinner when they go higher. The same will happen to us if we go high enough. If we go up about 1,200 kilometers from the earth, we'll find no air there. Some birds can fly into the sky as high as a plane, but they cannot fly or live without air.

    Looking up above us, you will see the blue sky with white clouds. It is usually light blue. The color would be bluer when you see on the top of a high mountain. And you will see fewer clouds in the sky between you and the sun. Sometimes the sky doesn't look blue. When the sun rises and falls, you will see red, orange and other colors in the sky, such are the most beautiful moments of the day.

    Who can see the colors of the sky high above the earth? The astronauts! They can see those beautiful colors of the sky from the outer space. However, before flying into the outer space, they sit in a spaceship high above the earth and there is no air at all. The sky would be that dark and its color would be black.

    Now you may understand that we see colors because the air scatters (使散射) the sunlight. Light travels through the air. Without air there would be no colors.

    Laughter is natural for people. We start to laugh at about four months of age. We start to laugh even 1 we start to speak.

    Laughter connects us with others. We laugh more when we are with other people. It's difficult to pretend to laugh. Laughter is 2. When people pretend to laugh, most people know it's not real.

    When do people laugh?

    Only 10 to 20 percent of laughter is about something 3. Most laughter is about being friendly with other people. Most laughter says, "I don't want to 4 with you. I want to be friendly with you." This kind of laughter brings people together.

    We often laugh when we feel nervous. In movies, there is often a joke at an exciting moment when everyone feels nervous. It is usually a(n) 5 joke, but we laugh a lot. Our laughter helps us 6.

    Why doesn't everyone laugh at the same joke?

    Not everyone has the same sense of 7. Some people think a joke is funny, but other people don't think so. People have different ideas about what is funny.

    Our idea of what is funny changes with 8. For young children, the world is new. They are interested in many things, so they laugh 9. Teenagers often laugh to protect themselves. Adults laugh at themselves and other people with similar problems. They laugh at things that give them stress. Our 10 for laughter change gradually.

House fires cause many deaths each year and a large number of these fires are unfortunately set by children.{#blank#}1{#/blank#}Kids must understand that they'd better not play with fire. You should keep matches and lighters out of their reach.

{#blank#}2{#/blank#} The main job of such an alarm is to protect you while you're asleep. You should have a smoke alarm outside each bedroom and on each floor of your home. You ought to have two plans for getting out of your house if there is a fire and practise these plans in the dark with your family.

A smoke alarm warns you of the danger. {#blank#}3{#/blank#}Take action immediately. When you come to a closed door, check it with the back of your hand. If it feels hot, there may be smoke or fire behind the door, so take care. Once you are out of your house, call the fire department from a neighbor's house. If a family member or a pet is caught inside, you shouldn't go back in. Firemen know how to perform rescues safely.

{#blank#}4{#/blank#} Change the batteries at least once a year. You should use the test button each month to see if the alarm and batteries are still working. A smoke alarm lasts about ten years. You ought to change it even if it seems to be working.

When somebody thinks of traveling, one of the first things that come to his mind is the beach. Beaches are among the favorite destinations (目的地) of many people. Here is a list of some must-see beaches.

Kauna'oa Bay, Hawaii

An amazing place in Hawaii, Kanuna'oa Bay is a crescent-shaped (月牙形的) beach that is famous for its clear, blue water and palm trees along its shores. This beach is best for travelers who love sunbathing, swimming and surfing. Located on this island is a historical hotel which gives the beach "Mauna Kea Beach" as its nickname (绰号).

Langkawi, Malaysia

Also known as "the land of one's wishes", the island of Langkawi is one of the best in Malaysia. It is known for white sand beaches with sandy bays (海湾). The beaches are also surrounded (围绕) by mountains of green forests.

St. Barts, France

Located in the Caribbean Sea, St. Barts is a world-class beach that is famous for its sand and greenish-blue waters. Rocks surround and protect the island as well as provide one of the best diving (潜水) opportunities for tourists. The beaches are rarely crowded, so it is perfect for travelers. It is one of the most visited places by rich travelers because of its beauty.

Fraser Island, Australia

This heritage (遗产) island in Queensland, Australia is a World Heritage site that is known to be the largest sand island in the world. It is also popular for its sand dunes (沙丘), forests and plants near its shores. The dunes are surrounded by grass and plants. This sand island is thought to be a paradise by tourists.

    If you had billions of dollars, would you donate almost all of it to charity? Well, that's what Mark Zuckerburg, CEO and founder of Facebook, just said he would do.
    Zuckerburg and his wife Priscilla Chan promised to give 90% of their Facebook shares to society. Right now that is about $45 billion, and they plan to donate the money to things like science and education.
    Many billionaires have done similar things. Bill Gates, creator of Microsoft, made The Giving Pledge, an activity in which billionaires promise donate more than half of their wealth to charities. This started in 2010, and now 139 people from 15 countries joined it.
    But giving back and helping others isn't just for big billionaires. People like Zuckerberg, and Gates may have more to give, but people with less are doing it, too.
    Especially around the holidays, people want to do their part and give back to people who are less lucky than them. Schools may have food collections where people bring a few food items, and together they can make a big donation to places like homeless people's homes.
    People also host special events like concerts of runs to be creative while raising money. Regular people donate whatever they can to US charities like the United Way and the American Red Cross.
    Then these charities are able to help US communities in different ways like education, health and improving the lives of the poor. These individual donations come together to make a big difference.

青春期是人生发展的重要阶段，成为更好的自己是每一位青少年的孜孜追求。学校英文报刊发起"成为更好的自己"的征文活动，主题涉及"与人相处"、"生活方式"、"学习习惯"、"兴趣爱好"、"独立自主"等方面。请你结合自身经历，谈谈如何成为更好的自己。内容包括：(1)从上述几个方面任选2项，谈谈自己的经历和计划；(2)呼吁大家珍惜当下，把握青春，做更好的自己；

作文要求：(1)不能照抄原文不得在作文中出现学校的真实名称和考生的真实姓名；(2)语句连贯，词数 80个左右。作文的开头已经给出，不计入总词数，也不必抄写在答题卡上。

At the stage of puberty, I am going to make myself better.