Rik-rrork. That's the sound made by frogs singing at night. You might have thought the noises were just the musical sounds of ure. You probably didn't realize that you were listening to frogs' communicating with one another. These familiar sounds are not random(随意的) but are actually meaningful to frogs.

Being Heard but Not Seen

    Frogs are good at being heard but not seen. These animals have several characters that protect them n predators (捕食者 ). One is their size. Most frogs are small, which helps them hide easily. Many frogs have coloring that allows them to hide in their environment, making it difficult for predators to find them. In addition, most frogs are active at night. So it is difficult for most animals to see them in the dark.

Small but Loud

    Frogs call to tell other frogs where they are. Their voices can be very loud. But when frogs feel the footsteps of a larger animal, they become silent.

    Many of the world's frogs live in rain forests, where there are many different animals calling to their own species (物种 ) in their own ways. Frogs need to call loudly enough to be heard through the noise in order to find other frogs.

Singing with Purpose

      Peter Narins is a scientist who studies how frogs call to one another. He has learned that frogs use their calls to help them tell friend from enemy. They sing the same notes at the same volume (音量 ) each time they call. In addition, Narins has found that frogs of the same species always sing the same patterns (模式 ). These patterns are like a code that is different from other animals' calls and difficult for others to copy. Narins also observed that timing plays a role in frog calls. Many frogs call only at a certain time of night.

More Work to Do

    Scientists want to better understand the purpose of frog calls. Studies continue to explore the details of frogs' unique communication. Being heard but not seen is one way frogs stay safe. The idea that they have found a way to survive in a dangerous world is simply amazing.

    People worldwide are doing something to protect the earth. As kids，we can also try our best to help. We can do the following.

    ●Change a light. Change a regular light to a more energy-efficient(节能的)light.

    ●Drive less. Walk, ride or use public transportation. Ask your parents to drive less. By this way, we can make less pollution.

    ●Recycle more. Think before you throw away trash. Throw trash into different trash cans, and this helps recycle.

    ●Use less hot water. It takes a lot of energy to heat water like a bath instead of a shower, and wash clothes in cold or warm water.

    ●Adjust(调节)your air-conditioning. Move it down 2℃ in winter and up 2℃ in summer than you want it to be. This helps save electricity.

    ●Plant a tree. Any tree can take away one ton of CO₂ through its lifetime.

    ●Turn off the electricity. Remember to turn off your TV, and cell phone charger(充电器)when not in use.

    This will help save electricity and reduce CO₂.

    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 scanned (扫描), 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 850kg of paper, saving 17 trees and 50 percent of water. Because of their benefits, some countries have developed successfully sorting systems.

    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 "recyclable (可回收利用的) waste" like steel and glass, and the green lid bin for "green waste", such as grass and leaves. On the street, the bins are printed with pictures of the things that are allowed inside. It makes recycling quite easy.

    I have a nice family. My parents love me very much. I have no {#blank#}1{#/blank#}（兄弟）and no sisters. but I have some cousins. This is Kate. She is my {#blank#}2{#/blank#}（叔叔的）daughter. She is a nurse（护士）. She likes{#blank#}3{#/blank#}（蓝色）, and her room is always very {#blank#}4{#/blank#}（整洁的）. She has a cat Mimi. {#blank#}5{#/blank#}（是）she and her cat in the room now? No, they are in the kitchen. And this is John. He is my aunt's son. He likes {#blank#}6{#/blank#}（模型）planes very much. They are{#blank#}7{#/blank#}（到处）.Tom is my aunt's son, too. He is a middle school student. He often helps me with my study. I {#blank#}8{#/blank#}（感谢）him very much for his help. Where is{#blank#}9{#/blank#}（他们的）mother? Oh, she is playing computer games. Two {#blank#}10{#/blank#}（手表）are on the desk, too.

    The summer holiday is coming. Try to take some time off from school and have fun. Here are some ideas for planning your summer holiday.

    First of all, joining a club is a good idea! You can join a music club, a sports club or an art club, it's good for your future and the teachers in the club can give you some good advice (建议). You can also make some new friends.

    Doing something good for society (社会) is also great. There are many volunteer programs(志愿者项目) for you to choose, such as looking after the____①___or the young, cleaning the streets, planting trees or keeping the traffic(交通) in order. You know that students can also make the world better.

    Did you ever live with another family? You can join in a program___②____"Meeting a New Family" .Two families exchange their children for some time so that they can learn how to get on well with others.

Summer camps are still popular today. An English summer camp can be a good one. You can not only make friends but also learn English.