Which file types can be specified to narrow search results?

The correct response is that all of the specified file types can be used to narrow search results effectively. When searching for resources or documents on the internet, you can utilize file type search operators to limit results to specific formats. This is particularly useful in educational and research contexts where you might want structured data, such as reports or papers in particular formats.

For example, using the file type operator followed by the particular format (such as "filetype:pdf" for PDF files) will return only those documents that are in the specified format. This capability enhances the efficiency of search queries, allowing users to filter through vast amounts of information quickly to find the most relevant documents that meet their format preference.

While the other options correctly identify individual file types that can be specified, none represent the complete range presented in this context. Utilizing the "All of the above" option encompasses the various document types available and confirms that any of these formats can be specified to refine search results.