Shortcut key to double underline the selected text is                 .

The correct answer is Ctrl + Shift + D because this specific combination acts as the standard global keyboard shortcut to apply a double underline style in Microsoft Word.

• Ctrl + Shift + D: This is the correct choice. Pressing these keys simultaneously targets the selected characters and draws a dual decorative underline rule beneath them without forcing users to navigate through the Font settings panel.


• Incorrect Options:
  
  
  
  • Ctrl + Shift + U: This is incorrect. In some Linux environments or specific text editors, this triggers Unicode entry fields, while standard Microsoft formatting bypasses it.
  
  
  • Ctrl + Alt + D: This is incorrect. This key combination is often mapped to system tasks like displaying the desktop or launching utility tools.