Often times the background of an image gives it away. Like things that should be rectangular but aren't. On images with plain backgrounds it can be a lot harder to tell sometimes.
I can't fly a plane. I can still tell when a plane has crashed. I can't play a sousaphone. I can still tell when someone's played an incorrect note with one. I can't cook Beijing roast duck. I can tell when one has been burned nonetheless, somehow.
It's almost as if the question isn't being asked in good faith.