ответ: 1. What have you been doing for a long time?
2. Who have been doing this work for a long time?
3. Have you been doing this work for a long time?
4. How much time have you been doing this work?
5. We have been doing this work for a long time, haven't we?
ответ: 1. What have you been doing for a long time?
2. Who have been doing this work for a long time?
3. Have you been doing this work for a long time?
4. How much time have you been doing this work?
5. We have been doing this work for a long time, haven't we?