More than millions of years ago, there were deserts. Now about one fifth of the Earth's surface {#blank#}1{#/blank#} (be) deserts. The size of the world's deserts keeps {#blank#}2{#/blank#} (change). Deserts can be hot or cold. The Australian Desert is a hot desert, while the Gobi Desert is a cold desert. A desert is a very dry land and there is hardly any rain. The Sahara Desert in Africa receives less than 1.5 cm a year. {#blank#}3{#/blank#} it doesn't rain very often in deserts, sometimes even for years, there can be heavy rain suddenly. Because they are dry, deserts have wide changes in temperature each day. When the Sun goes up, it is very hot, even hot enough {#blank#}4{#/blank#} (fry) an egg on the ground. At night, the heat that {#blank#}5{#/blank#} (receive) by the ground during the day disappears {#blank#}6{#/blank#} (quick), and then it gets {#blank#}7{#/blank#} cold that water would turn into ice. Because {#blank#}8{#/blank#} the change, living in the desert is very difficult. Man can make deserts, but man can also stop {#blank#}9{#/blank#} (they) from getting larger and larger. Planting trees can prevent the sand from {#blank#}10{#/blank#} (spread).

    Deserts are found where there is little rainfall or where rain for a whole year falls in only a few weeks' time. Ten inches of rain may be enough for many plants to survive (存活) if the rain is spread throughout the year, If it falls within one or two months and the rest of the year is dry, those plants may die and a desert may form.

    Sand begins as tiny pieces of rock that get smaller and smaller as wind and weather wear them down. Sand dunes (沙丘) are formed as winds move the sand across the desert. Bit by bit, the dunes grow over the years, always moving with the winds and changing the shape. Most of them are only a few feet tall, but they can grow to be several hundred feet high.

    There is, however, much more to a desert than sand. In the deserts of the southwestern United States, cliffs (悬崖) and deep valleys were formed from thick mud that once lay beneath (在……之下) a sea more than millions of years ago. Over the centuries, the water dried up. Wind, sand, rain, heat and cold all wore away at the remaining rocks. The faces of the desert mountains are always changing--very, very slowly--as these forces of nature continue to work on the rock.

    Most deserts have a surprising variety of life. There are plants, animals and insects that have adapted (适应) to life in the desert. During the heat of the day a visitor may see very few signs of living things, but as the air begins to cool in the evening, the desert comes to life. As the sun begins to rise again in the sky, the desert once again becomes quiet and lonely.

In China, very few children make pocket money. However, in western 1 , such as the UK, the US, Italy and France, most kids make pocket money by themselves. They make money in many different 2 . When kids are very young, their parents help them 3 the fruits of their own trees to neighbors. Kids may also help 4 do housework to make money at home. When they 5 sixteen, they can make money by sending newspapers or by working in fast food restaurants, 6 during the summer holidays.

There are many advantages of making pocket money by kids themselves. First of all, they learn the 7 of money by working hard so that they will not waste any. Secondly, they learn to 8 money to buy things they need or want, such as books, pencils and even clothes they like. Thirdly, they learn to 9 the daily life problems by helping their parents or others. Making pocket money is 10 for children when they grow up. That is why parents encourage their kids to make pocket money.

The 14^th China Airshow was held from November 8^th to 13^th in Zhuhai. More than 42 countries took part in the show, including the United States, the United Kingdom, Australia and many other countries. Among the different models of airplanes, the J-20 Drone（无人机）took many people's breath away.

The drone is one of the greatest inventions in recent years. A drone is light and portable, which makes it possible to be put in a backpack easily.

Some small drones are widely used for taking photos and putting on light shows. Other larger drones are used to carry things to far places in a smart way. For example, Mei Tuan Takeout（美团外卖）uses drones to send food or packages to people's offices in Shenzhen. The delivery time has been greatly cut down. Drones can be also set to finish tasks for farmers. They can spray pesticide and check whether the crops are growing well at different time of a day. So, a farmer can look after land five time larger than that before. Scientists are also using underwater drones to get information on CO₂ levels in the ocean. It's the newest way to study the ocean's condition and improve（改进）its environment.

Project- based learning (项目化学习) is learning while doing. It gives learners the chance to get a deeper understanding of a topic. During the learning, learners solve problems by using real- world examples and challenges. Project- based learning is becoming widely used in schools. Students work on a project over a period of time— from a week to a term. At the end of the project, they show their knowledge and skills by creating a product for people. Let's take the example of Sandra.

Sandra is an eleven- year- old student in Sunshine Primary School. She wanted to know more about Greek mythology (希腊神话). Well, how did she make it?

From the example of Sandra, we can see that project- based learning allows a student to learn about a topic and then create a project based on his or her talents and skills. Not everyone is a great test taker, but everyone is good at something. Through project work, students can not only learn deeply about a topic, but also have fun learning. So if you' re interested in something, why not start with project- based learning?