Access keys provide a way to quickly use a command by pressing a few keystrokes, no matter where you are in the program. Every command in a program that uses an Office Fluent ribbon can be accessed by using an access key. You can get to most commands by using two to four keystrokes.
Press and release the ALT key.
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The KeyTips are displayed over each feature that is available in the current view. You can then select other keystrokes such as P for Print.
Source: Really Useful Website