写出一个负无理数____ 

    It was my first day in Hangzhou, the Chinese city famous for its ____ (nature) beauty and history and I didn't have much time to spare. I wanted to see ____ much of the city as possible in the two days before I was to return to Guangzhou.

    My first task was to decide where to go and how to get there. I took out my guide book ____ there was a lot of information about the city's well-known tourist ____ (attraction) and started to read. At that moment, an attractive young lady who noticed my book came up ____ me and introduced herself. She said her name was Bai Li and ____ (kind) offered to show me around the city. I was delighted and was about to accept her suggestion when she ____ (suggest) we first go to the West Lake and walk along the Broken Bridge.

    I liked the idea of visiting the West Lake, but wasn't so sure about crossing the Broken Bridge. If it was broken, did she expect me ____(jump) across? And I couldn't swim, so if I fell in then I ____ (die). That was definitely not an attractive idea, so I politely declined her ____ (invite), closed my book and walked away.

“用微观的眼光看世界”是我们学习化学的重要思想方法．试根据以下材料，结合你所学过的知识，简要回答问题：

材料一：一滴水里大约有15万亿亿个水分子，如果10亿人来数一滴水里水分子，每人每分钟数100个，日夜不停，需要数3万年才能数完．

材料二：大多数物质都有热胀冷缩的现象．

材料三：湿衣服在夏天比冬天容易干．

（1）材料一说明：____；

（2）材料二说明：____ ；

（3）材料三说明：____ ．

京杭运河是世界上开凿____，规模____，里程____的人工航道。