To complete these sentences, we need to determine whether to use the past simple or the past perfect tense. The past perfect is used to describe an action that was completed before another action in the past. The past simple is used for actions that happened at a specific time in the past. Let's analyze each sentence:
When the police arrived, the car had gone.
- The car leaving happened before the police arrived.
When I got to the shop, it had closed.
- The shop closing happened before I got there.
They had eaten everything by the time I arrived at the party.
- The eating was completed before I arrived.
When we left the beach, the rain already had started.
- The rain starting occurred before we left.
I had tried telephoning her several times but she had left the city.
- Both actions (trying to call and leaving the city) were completed before the present moment being referred to.
When I found the purse, someone had taken the money out of it.
- The money was taken before I found the purse.
The car had gone when I looked into the street.
- The car leaving occurred before I looked.
All the garages had closed by the time we crossed the border.
- The garages closing happened before we crossed the border.
You already had left when the trouble started.
- You leaving happened before the trouble started.
I was sorry that I had not been nicer to him.
- The realization of not being nice happened before the feeling of being sorry.
Nobody came to the meeting because Angela had forgotten to tell people about it.
- Angela forgetting happened before the meeting.
I had seen her before somewhere. — I knew.
- Seeing her happened before knowing.
She couldn't find the book I had lent her.
- Lending the book happened before she looked for it.
All the people we had invited turned up, and some that we had not invited.
- The inviting happened before the turning up.
When she came in, we all knew where she had been.
- Her previous location was known before she came in.
In all these sentences, the past perfect is used to indicate an action that occurred before another action in the past, which is indicated by the past simple.