Question: What is the last step in extending XHTML modules?

1. The last step is to complete the extension of XHTML compound documents and make sure the documents adhere to the defined namespaces.
2. The last step is to create the DTD for the XHTML extension, which references both the XHTML modules and the new modules.
3. The last step is to run the XHTML extension through the XSLT processor, which will properly format it.
4. The last step is to verify that the XHTML is well formed and valid, and compatible with most browsers.

Answer: The correct answer of the above question is Option B:The last step is to create the DTD for the XHTML extension, which references both the XHTML modules and the new modules.