上楼、下楼和在路上行走我们都应靠（    ）边走。

阅读短文，选择正确的答案。

    I'm a lovely girl. You can call me Li Li. I like the blue sky and white cloud. I also like colourful flowers. I love my family. I love my father and mother. I go to school from Monday to Friday. Our home is near the school. We have a house. It is a clean and beautiful house. The house has three rooms. One is a living room. The other two are bedrooms. In the living room,  there is a table and six chairs. There are some flowers on the table. There is a garden in front of the house. I often play games and take pictures in the garden. Our house isn't big, but we like it.

2014 年 12 月 12 日，南水北调中线____工程正式通水。（）