She was visiting her dentist at two o’clock yesterday. (Whom? When?)
Whom was she visiting at two o`clock yesterday? When was she visiting her dentist?
They had an English lesson yesterday. (Who? What lesson?)
Who had an English lesson yesterday? What lesson did they have yesterday?
He was painting the roof of the garage last Saturday. (Who? What? When?)
Who was painting...? What was he painting...? When was he painting...?