This key combination collapses the ribbon.

The correct answer is option (1) : [ctrl]+[F1].

Ctrl key: The Ctrl key is often used in combination with other keys to perform specific actions within software programs.
F1 key: The F1 key is frequently used as a "help" function in many programs.

In this case, the combination with Ctrl acts as a specific shortcut for manipulating the ribbon. Therefore, pressing Ctrl + F1 together triggers the action of collapsing the ribbon, giving you more screen space for your document or workspace.