Kei te aha?

Kei te aha…? is used to ask a person what they are doing.
Personal pronouns are used when addressing whoever and however many people you are talking to. This includes koe, ia, rāua, māua, tāua, kōrua, rātou, mātou, tātou, koutou.

Kei te aha kōrua?
What are you two doing?

Kei te aha…? can also be used to ask a person what someone else is doing. This is done by using a before the person's name.

Kei te aha a Hata?
What is Hata doing?

It is also appropriate to address the person(s) you are talking to by name or to use terms of address. This is done by using e appropriately followed by the name or term that you wish to address the other person by.

Kei te aha rāua, e Hata? What are those two doing, Hata?

The correct response to this question is, Kei te followed by the activity the person is doing, e.g.

Kei te aha koe?	What are you doing?
Kei te tākaro kēmu ahau.	I am playing games.
Kei te aha a Hata?	What is Hata doing?
Kei te kohikohi moni ia.	He is fundraising.

Further explanations and exercises: Te Kākano pp. 12-14; Te Kākano Pukapuka Tātaki p.13.

Pātai atu ki ngā tāngata kei te aha rātou.
Ask the characters what they are doing.

Mā ngā tāngata koe e pātai atu kei te aha rātou. Whakautua ngā pātai.
The characters will ask you what they are doing. Answer the questions.