2 When Sue came back home, the floor was clean. (her sister/ mop/floor)
3 John didn't want to eat. (he/already/have/lunch)
4 We invited Ann out but she couldn't come. (she/arrange/to go
out with/parents)
5 Helen asked Laura to go to the cinema with her, but she
refused. (she/see/film/before)
6 When Tom arrived, Stella was very angry. (she/wait/for an
hour)​

2. When Sue came back home, her sister had mopped the floor. Explanation: The past perfect tense is used here to indicate that the action of mopping the floor happened before Sue came back home. We use the past perfect tense (had + past participle) to show that one past action happened before another past action. 3. John didn't want to eat because he had already had lunch. Explanation: The past perfect tense is used here to show that John ate lunch before the time being referred to. "Had already had" means that he ate lunch in the past, prior to the specific time mentioned. 4. We invited Ann out but she couldn't come because she had already arranged to go out with her parents. Explanation: The past perfect tense is used here to show that Ann made plans with her parents before the invitation was extended. "Had already arranged" indicates that the arrangement was made in the past, prior to the event being discussed. 5. Helen asked Laura to go to the cinema with her, but Laura refused because she had already seen the film before. Explanation: The past perfect tense is used here to indicate that Laura watched the film prior to the invitation to go to the cinema. "Had already seen" means that she watched the film in the past, before the specific time mentioned. 6. When Tom arrived, Stella was very angry because she had been waiting for an hour. Explanation: The past perfect continuous tense is used here to show that Stella had been waiting for an hour before Tom's arrival. "Had been waiting" indicates a continuous action that started in the past and continued up until a particular point in the past.