Formal:
* আপনি কী করছেন? (Aapni ki karchen?) - This is the most formal and polite way to ask.
* আপনার কি কাজ আছে? (Aapnar ki kaj ache?) - This literally translates to "Do you have any work?", but it's used similarly to "What are you doing?".
Informal:
* তুমি কি করছো? (Tumi ki karchho?) - This is the informal way to ask a friend or someone you know well.
* কি করছো? (Ki karchho?) - This is the very informal version, typically used with close friends or family.
* কি চলছে? (Ki cholche?) - This literally means "What's happening?", but it's a common way to ask "What are you doing?".
Note: When talking to someone older or of higher social standing, use the formal forms. When speaking with someone younger or of equal standing, you can use the informal forms.