假设你是李华。你的美国笔友Susan要在暑假来中国桂林参加一个文化交流活动。 她想提前了解一下这座城市的相关情况，写信向你询问，请根据以下提示信息，给她回一封信。

注意： 1）词数100左右，开头和结尾已经给出，但不计入总数；

2）可适当增加细节，以使行文连贯；

3）参考词汇   象鼻山 Elephant Trunk Hill   chilli sauce

Dear Susan,

I'm glad that you are coming to Guilin for an exchange program during the summer holiday.

Yours

Li Hua

注意：1.词数120左右；2.可以适当增加细节，以使行文连贯；3.开头和结尾已给出，不计入总词数。

    The way people spend their holidays changed a lot from 2006 to 2016.

    There was a boss who made a contract with his workers: he will pay their salary each week, but not in cash. Instead, the workers would choose some goods in a shop, which equal the value of their salary. Then he will pay the cash to the owner of the shop.

    But one day, one of the workers complained to his boss, “The shop owner said 'no cash, no goods'. And he requested us to pay in cash.” For that reason, the worker asked the boss to pay him in cash, too. The boss agreed. After a while, the shop owner came to the boss, asking him to pay for his workers.

    The boss was confused and looked into the issue, and finally found out that the worker told a lie. However, he paid the shop owner as usual, because he must keep his promise, even he was cheated and had to pay more money.

    Good merchants won't scrap(废除)their contracts. They won't sign contracts easily and usually chaffer(论价)for their benefits if they have to sign them. But after that, they will definitely follow them whatever the price.

【写作内容】

用约30词概述上文内容；

结合高中生活，简要分析你对契约精神的理解(不少于两点)；

你的启示和打算(不少于两点)。

【写作要求】

可以参照阅读材料的内容，但不得直接引用原文中的句子；

作文中不能出现真实姓名和学校名称。

【评分标准】

概括准确，语言规范，内容合适，语篇连贯。

What comes first: the optimism or the good health?

    Optimism, defined as the general expectation that the future will be favorable, could provide ways to improve health, some researchers believe. But scientists remain unsure if optimism goes ahead of health improvements, or vice versa.

    A recent study suggests that most people can't help but to think optimistically. This study was conducted by Ed O'Brien, a social psychologist at the University of Michigan in Ann Arbor. The findings suggest that people have a natural tendency to think positively about their future.

    Participants were asked to create a list of imaginary personal experiences that would make them happy or unhappy over the course of the next year. They then ranked how difficult it was to plan that list and how happy they believed they would be in the future overall. The easier it was for people to think of positive future experiences, the happier they imagined they would be. However, there was no relationship between easily developing negative future experiences and expecting to be unhappy as a result.

    O'Brien concluded that people seem to discount the possibility that future negative events will make them happy overall, suggesting that optimism might come more naturally. "We're not as used to thinking about the future in terms of things that are going to go wrong." O'Brien's study is one of many to find that people are consistently optimistic about their future, predicting pleasant experiences and discounting unpleasant ones. If optimism may lead to better health and people generally tend to think optimistically, what does this mean for the connection between mental and physical health? "If we can make sure that optimism comes before healthy states, we might be able to involve and improve people's optimism," Boehm explained. However, it's difficult to determine what comes first: the optimism or the good health.

The Possible Health Dangers of Air-conditioners

Although many of us may feel air-conditioners bring relief from hot, humid or polluted outside air, they pose many potential health hazards. Much research has looked at how the movement of air inside a closed environment—such as an office building—can spread disease or expose people in the building to harmful chemicals.

    One of the more widely publicized dangers is that of Legionnaire's disease, which was first recognized in the 1970s. This was found to have affected people in buildings with air-conditioning systems in which warm air pumped out of the system' cooling towers was somehow sucked back into the air intake, in most cases due to poor design. The warm air, filled with bacteria, was combined with cooled, conditioned air and was then circulated around various parts of the building. Studies showed that even people outside such buildings were at risk if they walked past air exhaust pipes.

    Large air-conditioning systems add water to the air they circulate by means of humidifiers. In older systems, the water used for this process is kept in special reservoirs, the bottoms of which provide breeding grounds for bacteria which can find their way into the ventilation system. The risk to human health from this situation has been highlighted by the fact that the immune systems of approximately half of workers in air-conditioned office buildings have developed the ability to fight off the organisms found at the bottom of system reservoirs. But chemicals called “biocides” are added to reservoirs to make them germ-free, and they are dangerous in their own right in sufficient quantities, as they often contain compounds strongly linked to cancers.

    Finally, it should be pointed out that the artificial climatic environment created by air-conditioners can also affect us. In a natural environment, whether indoor or outdoor, there are small variations in temperature and humidity. Indeed, the human body has long been accustomed to these normal changes. In an air-conditioned living or working environment, however, body temperatures remain well under 37℃, our normal temperature. This leads to a weakened immune system and thus greater exposure to diseases such as colds and flu.

1）学生垃圾分类的意识仍然较弱;

2）垃圾分类的重要意义;

3）垃圾分类应该从校园做起。