It is easier to float in the ocean than in a swimming pool. Do you know why?

    Ocean water is full of salt - and salt water can hold up more weight than fresh water. See for yourself! (Ask an adult to help you.)  You will need: 3 cups warm water; A wide-mouth jar（罐）; Salt; A spoon; A potato. You will do: 1. Pour 1.5 cups of warm water into the jar. 2. Add 1/3 cup of salt.  3. Stir(搅拌) until the salt is completely dissolved(完全溶解) 4. Add another l.5 cups of water. Pour it slowly over the back of the spoon into the jar so that the two kinds of water will not mix together. 5. Softly place the potato into the jar. Don't drop it. What will happen: The potato will sink - but only halfway! Why: Salt water is heavier than fresh water, so it will stay on the bottom. The fresh water will remain on the top. The potato is heavier than the fresh water, but it is lighter than the salt water. That is why the potato will sink only halfway down.

    It's hard to turn down a tasty banana. They taste good and you don't have to wash them before eating them. However, British scientists say that the fruit may disappear by 2050.

    One reason for this is climate(气候) change. Scientists at the University of Exeter collected data(数据) from 27 countries and regions that produce 86 percent of the world's bananas. They found that climate change has improved growing conditions in 21 of these countries. In the past 60 years, the average yield(平均产量) has reached 1.37 tons of bananas per hectare(公顷).

    However, if temperatures keep rising, this advantage will disappear. Ten of the countries, including India, the world's biggest producer of bananas, will produce fewer bananas. By 2050, the fruit may die out.

    Shouldn't bananas grow more easily if it's hotter outside? In fact, the perfect temperature range for growing bananas is between 24 and 32 C. If temperatures get too high, they will stop growing.

    Diseases are another danger to bananas. Unlike other crops, the bananas we grow come from shoot cuttings(茎段) rather than seeds. This means that all banana plants have the same genotype(基因型). In other words, if a disease is able to kill one plant, it could kill them all.

    One serious disease is called Panama. Caused by fungus(真菌) in the soil, it spreads easily. It has spread across South Asia, Africa, the Middle East, and Australia. If one banana plantation(种植园) suffers from the disease, it will take 30 years until it is able to grow bananas again. Scientists have yet to find a cure for this disease.

①Most people who move to a foreign country may experience a period of time when they feel very homesick and have a lot of stress. This feeling is often called "culture shock (文化冲击)". It is important to understand it and learn how to deal with it if you want to adapt successfully to your new home's culture.

②There are four stages that you will experience after you move to a foreign country. The first stage is usually referred to as the "excitement" stage. When arriving in a new environment, you'll be interested in the new culture; everything will seem exciting and everyone will seem friendly.

③But it won't be long before you move from the "excitement" stage to the second stage. The excitement you felt before changes to stress. It seems that everything is difficult. The language is hard to learn, friends are difficult to make, and even simple things like shopping have become a challenge. It is at this "stress" stage that you are likely to feel worried and homesick. This is the stage which is referred to as "culture shock".

④However, culture shock doesn't last for very long. If you are one of those who solve it successfully, you'll move to the "recovery" stage. At this stage, you start to understand and accept the way things are done and the way people behave in your new environment.

⑤The last stage is the "home" stage. This is the stage when you start to feel at home in the new culture. You start to learn from your new home and to like something of the new culture better than those of your own culture.

⑥Culture shock is normal. Everyone in a new situation will go through some form of it. Continue to be brave! And overcoming culture shock will be a piece of cake.

Everyone knows a power nap(小睡) feels good. If power naps fit right into your normal sleep/ wake cycle(周期), they can really help you get through the day.

Our bodies have a timekeeper called the circadian rhythm(昼夜节律). It helps you fall asleep, wake up, and feel more or less tired throughout the day. It also changes during the day, as shown in the picture below.

As we can see, the circadian rhythm is low between 2:00 and 4:00 pm. To improve your attention, productivity and memory, a power nap may be the answer.

In studies, a 10- minute afternoon nap is the best in improving your energy. And, it makes sense to nap around 2:00 pm.

Besides the length and the timing, there are other ways to have power naps:

●Try deep- breathing as you start.

●Choose a quiet, darkened place. A sleep mask may help.

●Lie down or sit in a comfortable chair.

●Listen to soft music.

●Give yourself a few minutes to refresh after your nap. Try a bit of stretching(伸展) and walking around.

A well- known poem by Tang Dynasty poet Du Mu tells of a scene (场面) in early April, "Rains fall heavily as Qingming comes, and passers- by with lowered spirits go. "

This scene takes place on Tomb- sweeping Day, also known as the Qingming Festival. Tomb- sweeping Day is a traditional Chinese festival. It began in the Zhou Dynasty, over 2, 500 years ago. 

Chinese people celebrate it to remember their ancestors (祖先). Tomb- sweeping Day became a public holiday in 2008. People have one day off for that day. 

On this day, families bring flowers, food and wine to the grave sites (墓地 ) of their ancestors. They place cakes, fruit in front of the grave and some may burn joss paper as money for the dead. After that, they sweep the tombs and cherish (怀念) the memories of their dead family members. 

Tom- sweeping Day gives us a chance to show respect to our ancestors and family members who have passed away and show that we miss them. This tradition shows that family values are an important part of Chinese culture. 

Tomb- sweeping Day is also the beginning of the time for gardening and outdoor activities in China. Families often get together for outings or to fly kites at this time. 

 Most children love to ride bikes. {#blank#}1{#/blank#} If you know the following rules, you' ll be safe. 

●{#blank#}2{#/blank#} There are many different kinds and sizes to choose from. When you buy a helmet, make sure it fits. 

●Ride along the right- handed side of the road if you aren't going to make a left turn or pass other people

●If you want to cross a busy street, you should get off your bike and wait for the light to change, and then walk it across the street. 

●Keep your eyes and ears open. Do not wear headphones. {#blank#}3{#/blank#} Stop at all the stop signs. 

● When you ride with a friend, do not ride next to each other. {#blank#}4{#/blank#}

●Keep your bike in good repair and clean. {#blank#}5{#/blank#} Or it could make you have an accident.