spacing of trees

例句：

1. 1. The distance between the two cities is about 300 kilometers.
   两座城市之间的距离大约是300公里。
2. 2.The teacher explained the concept of spacing in his lecture.
   老师在他的讲座中解释了空间的概念。
3. 3. The book has a spacing of 1 inch between each page.
   这本书每页之间有1英寸的间距。