Ответ:

  1. A: Did you manage to catch the 8 o’clock train last night? B: No, it had already left when I got there.

  2. A: What did Helen do when she arrived home? B: Well, she made something to eat and then she went to bed.

  3. A: Why was Sarah so upset last night? B: Before she came to find us, she had got in a fight with her sister.

  4. A: Did the children see their father yesterday? B: No. By the time he drove back from the city, they had already fallen asleep.

Past Perfect обозначает действие, которое произошло раньше другого действия в прошлом; Past Simple — более позднее действие или последовательность событий. Перевод: «Тебе удалось поймать поезд в восемь часов прошлой ночью? — Нет, он уже ушёл, когда я пришёл туда».