The key to exercise solutions in chapter 3c - Grammar in use for the textbook On Screen B1+/B2 - Student's Book with authors Virginia Evans and Jenny Dooley from Express Publishing
Question
Make sentences as in the example.
Answer
I had been riding my bike for an hour when I got a flat tyre. / I had been riding my bike for an hour when it started raining.
I was shopping for souvenirs when I lost my passport. / I was shopping for souvenirs when someone stole my wallet. / I was shopping for souvenirs when it started raining.
We had been waiting for hours before our flight departed. / We waited for hours when we got a flat tyre.
I had been lying by the pool when it started to rain. / I was lying by the pool when someone stole my wallet. / I was lying by the pool when I lost my passport.
I had been waiting at the airport when someone stole my wallet. / I was waiting at the airport when my flight departed. / I waited at the airport and then the flight departed. / I was waiting at the airport when I lost my passport.