`1`. When I arrived, Jack had left the office.
`2`. While I was having lunch, someone rang the bell.
`2`. The last time I was to the dentist was 6 months ago.
`3`. She began studying Japanese 5 years ago.
`5`. After he had done all his work, he went home.
`6`. After Steven had saved enough money, he bought a new motorbike.
`7`. When we tidied the house, the guests had left.
`8`. It's ages since I last heard from them.
`9`. Our dog bit the postman.
`10`. Who does this suicase belong to?
`12`. Everybody was astonished by Alice's strange ideas.
`13`. When is your birthday?