Respuesta :

1. How long have we been waiting for her?

2. How long has she been learning English?

3. How long have they been going out with each other?

4. How long have you been exercising?

5. How long has he been sitting there?

Para poder hacer una oración interrogativa se utiliza la siguiente fórmula

Verbo auxiliar ( Have or has ) +Not or haven't or hasn't + "Been" + verbo con "ing" + complemento