A recent study found people's lives are made shorter in North China. It is showed the life expectancy(平均寿命) had been cut down by 5.5 years there. Researchers（研究者）think that the heavy air pollution in China should be to blame(承担责任). It's really the truth. Our government has already done something. However, it doesn't seem to work so well.

    “Air pollution in China is doing harm to people's health. The harm is much more serious than we can imagine,” said Chen Yuyu of Beijing University, one of researchers of this study.

    Dirty air brings serious problems in North China. In January this year, the air pollution was worse than that in other places. That was caused by rising temperature and waste gas（气体）from coal heating（燃煤）.

    Chinese government should strongly fight with air pollution. They should think of more proper ways to deal with the problem. People should be encouraged to take buses, ride bicycles or walk, instead of driving cars. The factories that pollute heavily should be closed.

    “We need to improve our environment, although it might be expensive. Protecting our environment means protecting ourselves,” Li Hongbin, another researcher of the study said.

    You can be proud of yourselves, even if you can only make one or two of these green changes. The goal here is to limit carbon dioxide and other greenhouse gases, which are closely connected to the big problem of global-warming (全球变暖).

    WAY 1: Bring your own cup to Starbucks. You'll get a 10-cent discount, and it's one less paper cup to end up in a dustbin. The store won't create more waste when they throw away a cup.

    WAY 2: Turn off your computer. When in standby mode, your PC is still using energy. Turning off a monitor (显示器) for 40 hours a week may only save $ 5 a month, but it reduces CO₂ by 750 pounds.

    WAY 3: Reuse plastic bags. Instead of throwing away 100 billion plastic bags a year, try and get a second, third, or tenth use out of them. Better yet, next time you shop, try a reusable bag. The amount of oil it would take to make just 14 plastic bags would run your car for one mile.

    WAY 4: Use recycled paper in the bathroom. Most of the toilet paper we use is made from trees found in forests. If every family replaced(替换)one roll of toilet paper with a recycled one, 424,000 trees would still be standing.

    WAY 5: Plant a tree. Adding green to your garden is beautiful and earth-pleasing. Just one tree will help make cleaner air and save the environment from 5, 000 pounds of hot carbon dioxide each year.

    With the development of the technology, 3D printing is becoming more and more popular. We are now able to print things such as clothing, musical instruments and even cars. People and businesses are able to create the things they need very quickly and easily by using 3D printers.

    But can you imagine printing food? Some scientists are trying a new way to get the dining experience by doing this. They hope that having a 3D printer in the kitchen will become as common as the oven or blender. Scientists say that they are easy to use: you simply have to choose a recipe (食谱) and put the uncooked "food ink" into a printer. You can also change the instructions to make the food you want. This means that it would be very quick and easy to create tasty and rich meals.

    Using 3D printers to create your meals would also be saving the environment. There would be less need for traditional growing, shipping and packaging processes as food products would be a lot quicker and better. For example, tree leaves and insects could be turned into tasty products! Printing food could also help people who have a swallowing (吞咽) trouble. They could program the printer to print softer kinds of foods so that they would not have difficulty swallowing them.

            It could take away many jobs, including those for growing, shipping and packaging food. Imagine a world where there was no need for growing or producing and the same tastes could be printed from an uncooked "food ink". Besides, traditional restaurants might lose business. Also, we have to consider: is it really possible to get everything we need from them?

    As we know, cooking and eating together with family and friends has long been a traditional and enjoyable activity. It is hard to imagine a world where the pastime of cooking is dead and meals can be created at the touch of a machine.

    The best time to collect green leaves is early in summer but not so early. The months of June and July provide the best leaf samples (样本) but you can find great leaf samples throughout the summer. To make a full colour collection, you have to collect leaves in autumn. I have seen many beautiful fall colour collections.

    When you select leaves for your collections, try to select leaves of about the same size and shape on the tree. Make sure you should collect the complete leaves.

    Remember, simple leaves have only one blade (叶片) or leaflet. Compound leaves have several or many leaflets. You must know these two kinds of leaves. Good leaf collections contain the entire leaf. That is a small part of the twig (嫩枝) with a lateral or terminal bud (芽).

    When you collect leaves in the field, you can place them between the pages of a magazine to protect them. And then, press them as soon as possible before you remove them from this magazine. You should dry the collected leaves carefully before placing them in a leaf press. Finally, place them in a leaf press. You should write down each leaf's name and these names should follow the leaves until the exhibition comes.

    Now there is too much garbage(垃圾) on the earth. Our planet is in danger, so it is urgent(紧迫) to classify(分类) garbage. How should garbage be classified? The following pictures may help you.