阅读材料，回答问题。

材料  中国第28次南极科学考察队凯旋。此次南极科学考察历时163天，圆满完成“一船三站”考察任务。“雪龙”号极地科学考察船安全完成天津港澳大利亚弗里曼特尔港中山站长城站阿根廷乌斯怀亚港中山站澳大利亚弗里曼特尔港上海的航行任务，总航程28000余海里，其中冰区航行3900余海里。

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Every four years, the greatest athletes from all over the world get together in one city to take part in the world sports meeting—the Olympic Games. The holy flame (圣火) is carried from one place to the next. In 2008, the holy flame was carried to Beijing, the capital of China.

When Beijing was chosen as the host city to hold the Olympic Games in 2008, all the Chinese people were very happy, excited and proud. They showed their excitement in different ways when they heard the news. Some people cheered, jumped and shouted.

    In Beijing we built a new Olympic village with hotels for athletes and stadiums for matches.

    "One World, One Dream" is our slogan for the 29th Olympics. It expresses the wishes of 1.3 billion Chinese people for a peaceful and better world tomorrow.

每年5月31日为世界无烟日，从今年1月9日起，我国承诺实现公共场所全面禁烟．吸烟有害健康，烟气中的一种有毒气体是（　　）