Web crawlers copy all the visited pages for the search engine to index.
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Crawlers can prevent some engines from harvesting email addresses.
A. 对
B. 错
The seed URLs are the crawl frontier.
A. 对
B. 错
The crawl frontier includes the seed URLs and all their hyperlinks.
A. 对
B. 错
URLs from the frontier need visiting only once.
A. 对
B. 错
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