There are many kinds of trees. All trees have roots. The roots hold trees in the ground. The roots soak up ( 吸收 ) water and food. Then trees get water and food from the roots. You can't see inside a tree. But you can study how water moves through trees.

    First, get a stalk ( 茎 ) of celery ( 芹菜 ) and cut off its end. Put red colour in a cup of water. Then put the stalk of the celery into the red water. Then we can see the red water moving up in the celery easily.

    After half an hour, take the celery out. Cut it in half. Your celery should be red. This is because the water moved up the stalk. Water moves through trees in the same way as it moved through the celery.

Nowadays, "toilet revolution" is a thing in China.China isinvesting seven billion yuan in the project.The money is spent building or upgrading(改进) toilets in 30,000villages.

Experts have agreed that a "toilet revolution" is very important.Bettertoilets mean healthier lives and better living standards.Better toilets can alsohelp encourage tourism and improve the economy.

"Toilet revolution" was started in 2015.Chinese president Xi Jinpingthen called for improvement to toilets across China.The government has investedmore than 1.6 billion yuan in the project since then.Nearly 70,000 toilets havebeen built or upgraded.By the end of 2017, 45 percent of rural residents (居民) had been usingstandard toilets.In 2013, that number was only 36 percent.

In cities popular with tourists, more expensive toilets have been built.Thesetoilets have ATMs, Wi­Fi and recharging (充电) stations for mobile phones.Some toilets, meanwhile, havebeen expanded (扩大). Now, they have special cubicles (隔间) for the disabled and adults with young children.

China, in fact, is not alone in focusing on toilets.According to Bill Gates'foundation, forty percent of the world's population doesn't have flush toilets.UNICEF(联合国儿童基金会) says atleast 1.2 million young children die of diarrhea each year.Contact with human wasteis the main cause.Gates says toilets of the future will be able to save 800 livesevery day.

Welcome to my classroom! I'm Tom. This is my schoolbag. I always put it on the desk, but now it's under my chair. It's black and white. Black and white are my favorite colors. My pencil box and books are in it. What's in the pencil box? A ruler, two pencils, a pen and an eraser are in it. The ruler is white. It's new. It is my friend Lucy's ruler. She has two, and she lends(借) one to me. The pencils are nice. One is black, and the other is red. The red one isn't my pencil. It's Jim's. The black pen is mine. It writes very well. The eraser is white. I take these things to my school every day. 

Imagine you are going to give a speech the next day.The night before, you spend a lot of time thinking about the possible mistakes you might make and whether you're prepared enough. Well, you might be overthinking. 

Overthinking means going over the same thought again and again, analyzing( 分 析 ) the simplest situations or events too much. 

According to The Conversation, overthinking comes from one of our primitive instincts(原始 本能). The primitive mind will always see things in the worst possible light.Our brains are always looking for threats(威胁), to make a plan to deal with those threats and keep us safe. 

Some people believe that overthinking may be helpful because it helps us look at a problem from every possible angle(角度) and get ready for what might happen. However, research suggests that overthinking can make us stressed, anxious(焦虑的) and depressed (忧郁的). 

What's more, overthinking might create problems with how you get along with others.As you think the worst, make incorrect guesses, or worry about every little thing others do and say, you might misunderstand their intentions(意图). 

So, instead of sitting and thinking about a problem again and again, you can distract(转移注意 力）yourself for a bit. Your brain might find better ways to solve the problem while you're doing something fun, like gardening(园艺), or even while you're sleeping. 

Also, when you find yourself overthinking, challenge these thoughts. Ask yourself if they make sense and think about other possibilities.It can be hard at first,but recognizing that you are overthinking can help you make a change. 

Being safe (安全的) is important to students. What do you have to do in a new place?

{#blank#}1{#/blank#} you go out, remember the three "W"s: Always tell your parents WHERE you are going, WHO you are going with and WHEN you will get back home.

Make sure you know where your home is and {#blank#}2{#/blank#} your telephone number is.

Say "No" loudly if someone wants {#blank#}3{#/blank#} (make) you feel unhappy.

Shout loudly and run away if someone makes you go with {#blank#}4{#/blank#} (he) or lets you do the things you don't like.

Some strangers (陌生人) look very {#blank#}5{#/blank#} (friend), but never talk to them and never take gifts from them. If you do, you'll be {#blank#}6{#/blank#}great danger.

If you get {#blank#}7{#/blank#} (lose) in a place, be careful of whom you ask for help. Ask a policeman or someone with {#blank#}8{#/blank#} child for help.

You may think it's not easy to keep safe. {#blank#}9{#/blank#} if you follow these {#blank#}10{#/blank#}(rule), you will be safe.