Which of the following statements is true about reference to files within HTML code?

The statement regarding reference to files within HTML code being reliant on files being in specific locations is true. In HTML, when referencing external resources such as CSS stylesheets, JavaScript files, or images, the file paths specified must accurately reflect the actual location of those files relative to the HTML document. This means you have to ensure that the specified path either points to a location on your server, a local directory, or a correct URL if the resource is hosted externally.

For example, if you are linking to a CSS file, the "href" attribute in the link tag must correctly indicate where that CSS file is relative to the HTML file. If the paths are incorrect or if the files have been moved without updating the paths in the HTML code, the linked resources won't load, leading to broken links or missing functionality in the web page.

The other choices emphasize requirements that don’t generally apply to referencing files in HTML: files do not need to be encrypted for standard linking, while files can indeed be referenced from various locations, but doing so still requires the correct specification of their paths, and dependency on external CSS alone is not a limitation imposed by HTML itself.