Here is how to make a model submarine (潜水艇) that dives (潜水) and comes up from water like a real one.

You’ll need:

●Plastic bottle       

●Tape (胶带)

●Four coins            

●Small scissors       

●Bathtub (浴缸)

●Thin rubber (橡胶的) or plastic tube (管子)

●Waterproof (防水的) modeling clay (黏土)—not real clay, which dissolves (溶解) in water

Ways of making it:

1. Cut two small holes on one side of the bottle. Tape coins to that side of the bottle. Remove the cap; fix the tube to the bottle with clay.

2. Fill the bathtub with water; put the bottle in and let it fill with water.

3. Gently blow into the tube and observe what happens. Stop blowing and close the tube with your thumb. Lift your thumb and watch what happens.

What happens?

When you blow, air pushes out water; the bottle becomes lighter and rises. The bottle sinks (下沉) when it fills with water and coins weight it down. Coins keep holes pointing downward, so air does not escape.

When you stop blowing and seal (密封) the tube with your thumb the bottle floats. When you lift your thumb, air escapes through the tube and the bottle sinks. A real submarine works this way, by filling tanks with air or water.

How to lower costs and improve the living quality?

There are numerous products posted on social media, and you might believe an electric toothbrush, Luna facial cleaning massager, a flight ticket to Phuket and so on will bring you a better life. But for many graduates or those who have worked for only one or two years, your income cannot keep pace with expense. 【小题1】 Here’s how:

Keep running or doing yoga

It seems to be a challenge to afford a fitness center costing over 10,000 yuan in annual fees or for a personal trainer. But you can buy a pair of sneakers or a yoga mat instead. Running in a park regularly or doing yoga at home using free online resources is definitely a type of quality life. 【小题2】

Go to museums or libraries

Chasing young good-looking stars, watching their films and buying expensive tickets for their concerts are popular with many young people. 【小题3】 You seem to fail to take into account a variety of exhibitions and resources updated frequently in major cities. Why not have a try? What you need to do is to choose themes that you are interested in, make an online appointment in advance and then enjoy your weekend.

【小题4】

For some young people, the easy and instant access and the discount codes of online shopping make it an addictive draw. Sometimes what you buy online is not what you really need and the demands are created by the producers. For example, many buy new clothing and they don’t wear. 【小题5】 Money is not the only thing that can drive your quality of living, but your optimistic attitude towards life and self-disciplined way of life are.

Homework is a problem for students all over the world. As a student, you have a lot of homework to do every day. 【小题1】 And it helps you understand important knowledge（知识）. Luckily, there are some things you can do to make homework less difficult.

【小题2】

Write your homework down in your notebook if you need to. Don’t be afraid to ask questions about it. Understand why you should do your homework.

【小题3】

Many schools have study libraries. The students can study there. It’s more interesting to study with your friends. But the more homework you finish at school, the less you'll have to do that night at home.

【小题4】

It is difficult to hold your attention（注意力）for too long. So take some breaks while doing your homework. Taking a 15-minute break every hour is a good idea for most people.

【小题5】

If you don’t finish your homework at school, think about how much you have left. It’s a good idea to make a homework plan, especially（尤其）when you want to enjoy sports or other activities.