Three possibilities depending on what pointing device you are using... - System Preferences > Trackpad > More Gestures — Uncheck the box labeled "Mission Control"
- System Preferences > Mission Control under Keyboard and Mouse shortcuts — check what shorcutkey is defined for Mission Control
- System Preferences > Mouse — check the settings for the various mouse functions. several can be set to launch Mission Control.
If we knew what it was we were doing, it wouldn't be called research, would it?
— Albert Einstein
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