1. Mary, whose children couldn't swim, said that there should be a notice up warning people. 
2. I'm sure you all know David, who is going to talk about careers. 
hoặc: David, whom I'm sure you all know, is going to talk about careers. 
3. I remember the day when I was afraid to use my new computer. 
4. Some people dream of a job which they can do without technology. 
5. Thank you very much for the present which you sent me. 
6. There wasn't any directory in the telephone box which I was phoning from. 
hoặc There wasn't any directory in the telephone box from which I was phoning. 
7. She refuses to use machines which makes her work more arduous. 
8. He paid me 5 for cleaning ten windows, most of which hadn't been cleaned for at least a year. 
9. The Earls of Euston, after whom Eust Station is named, were landowners in London.. 
10. Emilia and I shared a room where/in which we spent nights talking.