The officially documented keyboard shortcut to insert a new worksheet in Microsoft Excel is Shift+F11. This command adds a new sheet to the left of the currently active sheet. An alternative shortcut for the same action is Alt+Shift+F1. The other options listed are not standard, default shortcuts for this function within Excel.

A. Ctrl+Alt+N is not a default keyboard shortcut for inserting a new sheet or any other common function in Microsoft Excel.
C. Ctrl+Shift+K is not a recognized default shortcut for inserting a new worksheet within the standard Excel environment.
D. Ctrl+Shift+N is a common shortcut in Windows File Explorer to create a new folder, not for inserting a new sheet in Excel.

1. Microsoft Support Documentation: "Keyboard shortcuts in Excel". Under the section "Work with worksheets," the official documentation lists Shift+F11 and Alt+Shift+F1 as the shortcuts to "Insert a new worksheet."

2. University of Wisconsin-Madison, Division of Information Technology: "Excel: Keyboard Shortcuts (PC)". This university resource lists Shift + F11 under the "Worksheet" category with the description "Insert a new worksheet."