Final answer:
To duplicate a selected object, the standard keyboard shortcut is Ctrl+D. Ctrl+C is used for copying and Ctrl+V for pasting, whereas Shift+D or Ctrl+Shift are not typically related to duplication.
Step-by-step explanation:
To duplicate a selected object in most software applications, you would typically press the Ctrl+D shortcut. This command is often used for the 'duplicate' function. While Ctrl+C is commonly known as the shortcut for 'copy', it does not duplicate an object within the application without then pressing Ctrl+V to 'paste' it. The combination of Shift+D or Ctrl+Shift is not commonly associated with the duplicate function.