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13. We enjoyed Mexico City where we spent our vacation. 

14. My friend whose first job was a secretary is now a personnel manager of a company. 

15. I saw several houses , most of which were quite unsuitable. 

16. The firm which I work for is sending me to New York. 

17. This is Mrs Jones whose son won the championship last year. 

18. I met Mary who asked me to give you this. 

19. We'll have to pass the entrance exam which will be difficult. 

20. That company has ten employees, all of whom are computer experts. 

21. Where are the students whose party we went to last night?

22. Valencia, which is due east of Madrid, is a great place. 

23. The Rodonda square, where they hold a market every Sunday, is near the cathedral. 

24. Sally has found a new job , which is lucky. 

25. These are the friends whom I met on my trip to Hawaii.