Sounds like your keyboard is glitching, usually caused by water. If so, kiss goodbye to your keyboard as it is unlikely it will repair itself. (Apple keyboards cannot stand water at all).
Open the virtual keyboard and check if any keys are held down or flickering. seems like your option key may be glitching.
To open the virtual keyboard, go to system preferences, go to keyboard, and check the box to show keyboard and character viewer in menu bar. Then click that and show the keyboard.
If it is the internal keyboard, then.... well.... that's tough... you probably would have to open it and disconnect the keyboard (and use an external keyboard). If you can, you should see an apple authorized repair representative center (whatever they call them).