PHP's filetype () function returns the type of the specified file or directory. The usage of filetype of search engine is file-type: file type. To search word documents, the file type is doc, so it should be filetype:doc；; "Site:" is followed by the site domain name, which limits the search scope to a specific site and looks for content on China Education Network, so the site domain name should be edu.cn. So the correct answer to this question is B.