The correct shortcut to view non-printing characters in most word processing software, including Microsoft Word, is typically Ctrl+Shift+8, which may appear as Ctrl+* on some keyboards. However, this can vary depending on the specific program and its version. It's always a good idea to check the software's official documentation or help resources for the most accurate and up-to-date information. In the context of LibreOffice Writer, the shortcut to show non-printing characters is Ctrl+F10. Therefore, the correct answer from the options provided would be 'd. Ctrl + F10'.
