The key to exercise solutions in chapter Unit 16 - Past perfect continuous for the textbook English Grammar in Use with authors Raymond Murphy from Cambridge University Press
Question
Read the situations and complete the sentences.
Answer
We'd been playing; it started
I'd been waiting; I realised (that) I was (in ...)
went; had been working / had worked
had been playing; started
I'd been walking for about ten minutes when a car suddenly stopped just behind me.