Formal:
* 你在做什么? (nǐ zài zuò shénme?) - This is the most direct and literal translation.
* 您在做什么? (nín zài zuò shénme?) - This is a more respectful version used when addressing someone older or in a position of authority.
Informal:
* 你在干吗? (nǐ zài gàn ma?) - This is a more casual and everyday expression.
* 你在干嘛? (nǐ zài gàn shénme?) - This is similar to the previous one but more common in spoken language.
Other Options:
* 你在忙什么? (nǐ zài máng shénme?) - This literally means "What are you busy with?" and implies that the person is engaged in something.
* 你在做什么事? (nǐ zài zuò shénme shì?) - This is similar to the formal translation but slightly more formal.
The best choice will depend on the specific situation and your relationship with the person you're speaking to.