题目内容
It's not difficult for a crawler to download the most relevant pages.
查看答案
搜索结果不匹配？点我反馈
更多问题
Designing a good selection policy cannot work with partial information.
During crawling, a crawler cannot get to know the complete set of Web pages, therefore it cannot design a good selection policy either.
Focused crawler or topical crawler is such a crawler to download pages similar to each other.
The anchor text of a link is an instruction to it.
微信支付 
支付宝支付