All of them can be used and almost all or all of them sound natural to me and appropriate depending on your sentece, it's very important for you to write a whole sentence so I can help you better. In this case the only answer I can think of is "progress". Ing endings emphasize that an action IS/WAS/WILL BE happenING. let me write a couple of examples for you. I was playing while the kid was jumping. Both things happened at the same time. While can be used in so many different ways many times it has the same meaning as when. I recommend taking a look at the Cambridge dictionary, grammar section and you'll find tons of examples.

Normally, "While + subject + verb + ing" or "while + subject + verb" makes connection between two sentences that happen at the same moment. For example: Simple Past: - My cellphone rang while I was taking a shower. - She left home while he was sleeping. Simple Present: - I study English while my brother sleeps. Simple Present Continuous: - I'm doing this while he is helping me with that. Well, I hope to have helped you. :) See you around!