1. The hold time is the amount of time a router treats a neighbor as reachable and operational. 保持时间是路由器把一个邻居视为可以到达和操作的一段时间。
2. Question3: from the perspective of contribution, I think maybe most common people are equally reachable. Right? 问题3：从贡献这个角度看，我觉得可能大部分普通人都差不多，是吧？
3. Make a site with a clear hierarchy and text links. Every page should be reachable from at least one static text link. 让网站有着清晰的结构和文本链接，所有的页面至少要有一个静态文本链接入口。
