Past perfect use
had + past participle (3rd form)
Examples for regular verbs ending -ed: look - looked, watch - watched.
arrived disappeared followed had opened waited
English Past perfect exercises
The past perfect refers to a time earlier than before now. So the past perfect is used to make clear that one action happened before another in the past.
Online exercises English grammar and courses
Free tutorial Past perfect.
English Past perfect exercises.
English grammar easy to learn. Past perfect matching exercises, English word order.