"Is this your first time leaving an unhelpful smart-ass reply?
Take it from someone with experience – it's important to make sure you're right before you hit 'Reply'. Otherwise you just look stupid."
I posted my experience.
That is, in 35 years of using Macs, I've never seen an "alt" key on a USA Mac (Apple-produced) keyboard.
I haven't seen it on 3rd party keyboards for Mac, either -- and I've used 3rd party Mac keyboards for at least 30 years (as well as Apple-produced keyboards).
I've never used a MacBook Air. Only MacBook Pros (and MacBooks, non-air).
Hence, my post 8 above to note my acknowledgement that at least a few Macs had "alt" keys.
If you don't like my postings, take it up with the management.