B

    When you hear westerners (西方人) say "Drop in anytime(随时来玩)"  or "Come and see me soon", you should realize that it doesn't mean you are welcome to come over to their house anytime. It's wise to telephone before visiting someone.

    Never accept an invitation unless (除非) you really plan to go. You may refuse (拒绝) by saying, "Thank you for inviting me, but I may not be able to come." If you are unable to come after accepting the invitation, be sure to tell those who invite you in advance (提前) that you will not be there.

    When you have accepted the invitation to a party or a dinner, it is polite to bring small gifts with you, such as bottles of drink, flowers and some others. Sometimes westerners may take you out to dinner in a restaurant and it does not necessarily mean that he is going to pay the bill at the end of the meal. He might want you to "go Dutch", which means each person pays his own bill.

    Scientists in Britain and the United States have made a new kind of enzyme(酵素) that eats plastics (塑料). With its help, plastics can be turned into smaller parts and go away quickly. Scientists believe that, in the future, it could solve the problem of plastic pollution.

    The enzyme is able to break down PET, a form of plastic. PET was first made in the 1940s and is now widely used to make plastic bottles. It can remain in the environment for many years and pollute large areas of land and water. So it has always been a headache to deal with the waste from PET and other plastics.

    The researchers made the discovery (发现) while examining the structure of a natural enzyme in Japan. They found that the natural enzyme was helping to break down PET plastics. So, they decided to make small changes to the enzyme by adding some amino acids (氨基酸). It made the natural enzyme's plastic-eating abilities work faster and better.

    John McGeehan, one of the lead researchers, said, "We've made an improved enzyme. It's better than the natural one. And we are trying to make more improvements to it." He went on, "The enzyme is not harmful to humans or animals, and it is friendly to the environment. So we are considering putting it into wider use."

    The team is now trying to make the enzyme break down PET in large quantities (大量地).

    "We'll see that the plastic pollution may be stopped with this technology. However, there is still a long way to go," John McGeehan added.

    A new rubbish sorting system (垃圾分类系统) has been put into use in Fangchengyuan Community in Beijing. Local people not only sort their rubbish, but also put QR codes (二维码) on it.

    "When the rubbish is collected and the codes are seen, I will get reward points to exchange for small gifts and even some money," one of the local people told reporters. "It's really creative and encouraging."

    This smart system has been carried out in 350 communities in Beijing. The capital of China has joined a list of cities in the country that take action to support rubbish sorting. For example, Shenzhen and Shanghai have made laws to punish people and organizations for not sorting rubbish correctly.

    China produces quite a lot of rubbish every year. Much of the rubbish is buried (填埋) in soil or burned without being sorted. Landfills (填埋场) take up a lot of land and have a risk of polluting the soil and water nearby. And burning rubbish can produce harmful gases. Through rubbish sorting, we can reduce the use of landfills and air pollution.

    What's more, rubbish sorting saves resources, which could bring economic benefits (经济利益). For example, a ton of waste paper can be reused to make about 850 kg of paper, saving 17 trees and 50 percent of water. Because of the benefits, some countries have developed successful sorting systems.

    Japan has a strict and detailed system. When people throw away a water bottle, the cap, the wrapper (包装纸) and the bottle itself have to go into three different bins. Every year, families receive special rubbish sorting timetables and directions from their local governments. They are advised to follow the timetables and directions when they throw away rubbish.

    In Australia, every family is provided with three rubbish bins—the red lid (盖子) bin for "general waste" like food and plastic bags, the yellow lid bin for "recycling" like steel and glass, and the green lid bin for "green waste" such as grass and leaves. On the streets, the bins are printed with pictures of the things that are allowed inside. It makes recycling quite easy.

Everyone needs friends. How do you have real friendship and keep it?

The American writer Sally Seaman tells young students some smart ways to find friends. Sally says finding friendship is just like planting a tree. You plant the seed（种子）and take care of it to make it grow. 

What makes a good friend? It s not because he or she has money or good looks. A good friend should be kind and patient（有耐心的）. For example, if you are in a bad mood, a good friend should listen to you and do his or her best to help you. 

But things can t always be happy. Even the best friends have fights （争 吵）. What should you do when you have a fight with your friend? You, d better talk to him or her. 

There are three steps（步）to be friends again： say sorry to him or her； tell him or her how you are feeling； tell him or her why you did this or that. Remember that friendship is the most important thing in your life. 

I see all the Spider- Man movies and Spider Man is always my favorite hero (英雄). This isn't because he could do anything. For example, he can't fly, unlike other superheroes, but he fights with bad people all the time. This makes him my favorite superhero.

I also like Peter Parker in the movie. He has the superpower(超能力) when he was just a student. He has to learn to be a common (普通的) person and at the same time, being a superhero is difficult for him, so he has to work hard. In many ways, he's very common. He has many of the same problems like other people. He is very shy. And he can't tell anyone about his story, and this makes him stay away from people.

I think everyone can learn something from Spider Man. He can't always make right decisions (决定), but every time he learns from his mistakes (错误). The important thing is that he always helps people in need. This makes him a true hero.