The document discusses the past perfect tense, which is used to link one past action that occurred before another past action. It provides examples of sentences using the past perfect tense structure, including sentences using "once", "when", and "until". It also gives examples of rewriting sentences to change them into the past perfect tense.

1. PAST PERFECT
Past perfect is used to link an action in the past with another past
action that took place later.
She had finished her homework when I called her.
PRESENTPAST
had finished called
1st action 2nd action
Once they had heard the explosion, they left the building inmediately.
PRESENTPAST
lefthad heard
1st action 2nd action
Past perfect is form by had + past participle

2. PAST PERFECT
Different past perfect structures
once + first action , + second action
Once he had washed the dishes, he went to sleep.
when + second action
, + first action
When we saw him last night, he had just come back from New York.
second action
(negative)
+ until + first action
He didn’t take part in the talent show until he had rehearsed enough.

3. PAST PERFECT
Rewrite the sentences using past perfect.
He put his apron on. Then he started cooking dinner.
He didn´t
1.
start cooking dinner until he had put his apron on.
2. The train left at 12:10. I arrived at the station at 12:15.
When I arrived at the station, the train had left.
3. I looked up all the words in the dictionary. Then, I answered the questions.
Just after I had looked up all the words in the dictionary, I answered
the questions.
4. The Mayor finished his speech. Afterwards, the town festivals started.
When The Mayor had finished his speech, the town festivals started.