1. it happened earlier than other events in the past
Angielskie słowo "Past Perfect" (it happened earlier than other events in the past) występuje w zestawach:
Love Research2. a letter had been written
Angielskie słowo "Past Perfect" (a letter had been written) występuje w zestawach:
czasy i gramatyka3. Past Simple
4. Present Perfect
5. Past Perfect
Use regret + gerund, if only + past perfect or wish + past perfect to say we want something in the past to have been different.