#80: Why did Mere drive to the supermarket?
he aha... i... ai?
Why did? — He aha... i... ai?
He aha ai? means “why?” because he aha means “what” and ai refers to the reason something happens. To ask why in the past, the structure is He aha + subject + i + verb + ai?. The particle i marks the past, asking what reason caused the action.