Нужно по этому предложению составить 3 вопроса вот предложение: they have already visited london this year.

Have they visited London this year?
When have they visited London?
What city have they visited this year?
Сойдет?

1. Who have already visited London this year? (вопрос к подлеж.)
2. Have they already visited London this year? (общий)
3. When have they visited London? (спец.)