14.It is very exciting to read his books
15.After she had eaten breakfast, she went to work
16.He doesn't forget to turn the light off before going out
17.When I arrived, Jack left the office
18.While I was having lunch, someone rang the bell

19.The last time I was to the dentist six months ago
20.She began to study Japanese 5 years ago 
21.After he had done all his work, he went home
22.Before Steven saved enough money, he bought a new motobike
23.When the guests left, we tidied the house