When the Audet family turns on the lights at Blue Farm, they are using electricity that comes from cows- cow manure(粪肥).

    Cows produce a lot of waste. One cow can create 30 gallons of waste each day. Now imagine the output of over 1,000 cows at Blue Farm. That's really a big amount.

    When farmers clean their barns, they put the waste together，and spread some of it on their fields for fertilizer(肥料). But now places like Blue Farm have a new way of using cow waste. They use it to produce electricity.

    Here's how it works: A big machine moves back and forth cleaning the barn floor. "The cows are animals of habit; they get used to it,and just lift one foot and then another to let it go by. "says Marie Audet.

    The machine pushes the manure into a big 600-gallon tank like a small swimming pool. The tank is called a digester(化粪池) because what happens there is just like what happens inside a cow: Bacteria(细菌) get to work and continue to digest the manure.

    Methane gas(甲烷;沼气) in the atmosphere is known as a "greenhouse" gas because it keeps heat just like a greenhouse does, causing our planet to warm up. That's an environmental concern. But the digester has a good result. Its gas is kept and used to power electric generators(发电机).

    At Blue Farm, the generators make enough electricity to power 400 homes. The Audet family sells the extra electricity they can't use themselves.

Chopsticks are a pair of small equal-length sticks, usually made of wood, used for eating Asian food. Chopsticks are mainly used in China. And it is believed that the first chopsticks were developed in China. Chopsticks play an important role in Chinese food culture. Chinese chopsticks are usually 9 to 10 inches long. They are round on the eating end which means heaven (天), and the other end is square which means earth. The appearance of chopsticks said goodbye to those days when our Chinese ancestors(祖先)had to use their hands to eat.      

Besides, the use of chopsticks has also been a part of Chinese food culture. There are some taboos that you must pay great attention to when you use chopsticks. Firstly, don't use them to hit your bowl or plate. Secondly, never use them to point at others. Thirdly, don't put them in different food without taking something. Fourthly, don't cross the chopsticks on the table. And lastly, don't leave your chopsticks standing in the rice. Chinese people do this only when they honor (尊重) the dead.

Nowadays, chopsticks have many new usages. For example, you can buy a pair as a gift to your friends and relatives. In Chinese, it reads "筷子", which means having sons soon, so a newly-married couple will be very happy to accept it as their wedding gift.

You might often use emojis(表情符号) when you talk to your friends online. But did you know when emojis came into our lives?

Before emojis, emoticons(颜文字) first appeared. Scott Fahlman was a teacher at Carnegie Mellon University, US. On Sept 19, 1982, he made history by posting"： —)" online. Guinness(吉尼斯) World Records called it the" first digital (数字) emoticon".

Over the past 40 years, emoticons and later emoji s became central to our online chats(聊天). GIFs and memes(表情包) also appeared. Now there are 3,600 emoji s for us to show our feelings, according to CNN.

Emojis are like our body language online. When we can't find the right words, emoji s can help. They make our chats more understandable. According to a 2017 study, emojis help us get the same happiness from online talks that we get from talking in person. Our brain sees them as language.

Emoji s change, too! Unicode brings new emoji s every year. And it cares about race (种族), gender(性别) and other things. In 2015, for example, it brought out emoji s with different skin tones(肤色). In 2016, emoji s about different jobs came out, with women's versions(版本) of them.

It's reported that 800 million people around the world have experienced back pain. And many of them find that their pain keeps coming back. ____ But scientists believe that doing one simple thing could help: walking. 

Scientists invited 700 people to take part in a study. Most were women and all of them had recently experienced back pain. The people were put into two groups. One group took part in a walking program and had six meetings with a doctor. People in this group were asked to walk half an hour five days a week, while those in the other group didn't do anything. The scientists followed up the two groups for three years. 

The scientists' findings are surprising. People in the walking group had an average (平均) of  208 days before their back pain recurred, while those in the other group felt the pain again after an average of 112 days. What's more, people in the walking group also made far fewer visits to the doctor. 

Why is walking helpful to lower back pain? Scientists are not yet certain of the reasons. But they think it's probably because walking can get the muscles (肌肉) stronger and improve sleep. As for how to walk, they suggest walking on a flat (平整的) surface. People also should listen to their bodies, as walking too far or for too long could make the pain worse. 

注意：（1）可在思维导图内容提示的基础上适当拓展信息。（2）不能照抄原文；不得在作文中出现真实校名和学生的真实姓名。（3）语句连贯，词数80 左右。作文的标题和开头已给出，不计人总词数。

My Friend and I

Everyone should have friends. Friends are important in our lives. My best friend is