Past perfect:

(+) S + had +PII + ....

(-) S + hadn't (had not) +PII + ....

(?) (....) Had + S +PII + .... ?

1. Kevin had gone home by the time I arrived.

2. Ethan suddenly realised that he had left his laptop on the train.

3. Mum was annoyed because I hadn't cleaned my room.

4. Had they studied English before they went to the USA?

5. We were hungry because we hadn't eaten.

6. My phone didn't work because I had charged it.

7. Why didn't you want to watch the film? Had you seen it before?

8. Sally was embarrassed because she had forgotten her dad's birthday.

9. I had never seen such a beautiful beach before I went to Kauai.

10. I did not have any money because I had lost my wallet.

11. Tony knew Istanbul so well because he had visited the city several times.

12. Had Susan ever studied Thai before she moved to Thailand?