Trees are one of the oldest " citizens (公民) " of our Earth. They keep our air clean, reduce noise pollution, improve water quality and provide food and building materials.

    Just like us, trees change a lot as they grow. At 1 to 3 years old, young trees learn how to protect themselves. For example, many trees grow thorns( 刺) to warn animals not to go near. Most young trees have large, deep green leaves so that they can catch enough sunlight and change it into their food and energy.

    When trees are 4 years old, they begin to grow very rapidly and become strong enough to face challenges later in life. At the age of 15, trees become young adults. They grow more slowly and begin to produce flowers and fruit.

    It is not until the tree is 20 to 25 years old that it becomes a real adult. The tree reaches its largest size. The adult tree gives us shade, oxygen and natural beauty; it is also a great place for a tree house, or a place for us to read a book, listen to music and so on. If we give the adult tree proper care, it will go on to live healthily for many years.

    Gradually, trees begin to grow older and older and even die. At this time, they still have their important place in nature. When a tree becomes hollow (空心的) or part of it becomes dead, it provides a home to small animals and is a source of food for many other animals.

    In many ways, the life of a tree is similar to our own life experience. When we are looking at the life of a tree, we learn about that each period of life brings its own form of joy and challenge.

    Enjoy every minute of the life of the trees and take care of the trees!

How to make ice-cream in a bag

    What you need:

    I spoon of sugar, 1/2 cup of "half and half" (牛奶和奶油的混合物)，1/4 spoon of vanilla extract(香草精), d add 1 spoon of sugar, 1/2 cup of "half and half" and 1/4 spoon of vanilla extract to the small bag.

    Next, add three glasses of ice 10 the big bag. You can add more or less just to make sure that the small bag will be covered by ice.

    Then, pour about 1/2 cup of salt into the big bag. The salt helps the ice get cold so you can add more if necessary.

    When it's ready, place the small bag in the big bag and seal tightly(系紧). You need to shake the bag for about five minutes.

    Finally, take the small bag out. Be careful not to open it. Wipe off(擦去) any salt on the bag. Now open the bag. You can enjoy your ice cream. You can finish all of the work in less than ten minutes.

难度系数：★★

Do you know that vocabulary is more important than grammar? If you have good vocabulary, you can communicate successfully, even if your grammar is not completely perfect.

However, one common problem is leaning new words and then forgetting them. So, when you want to use a new word in a conversation, you can't remember it at that moment. Does this often happen to you? The reason for this difficulty is that most students try to learn vocabulary by studying word lists and dictionaries and remembering the words. But it may not work if you don't have a very good memory.

The best way to learn vocabulary and remember the words successfully is to learn new words and use them at once. You can do this with a very simple exercise. Each time you learn anew word, for example, from an English lesson or an article, write it down in your vocabulary notebook. Writing is more active than just reading a definition(释义). You should write the word, the definition in English or translation, one example sentence from the article or dictionary and one example sentence that you create.

Imagine you just learn the word "generous", write in your vocabulary notebook: generous(adjective), definition-giving or willing to give freely. Example One, from the article: Thanks for paying for my dinner, you're very generous. Example Two, my example: My brother is generous because he volunteers at the animal shelter on weekends. It's best if your example sentences are true to your life, because this creates a personal connection with the new word. The next day, read your vocabulary notebook again and try to add one more example sentence using the new word. It's helpful for you to remember it. These two simple steps-writing the word and using it at once-help you remember and use new words.