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Using a wireless keyboard is not recommended for this because the keyboard doesn't connect immediately like a wired keyboard would. But, you can try anyway. On a PC keyboard, the Alt key is Option and the Windows key is Command.
If you are only getting sound from your headphones and nothing when you unplug them, try those steps first. If it still doesn't help, try inserting and removing the headphones a few times. There is a trigger inside the headphone jack that might be stuck,fooling the computer into thinking that the headphones are plugged in when they are not.