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Here are the answers: 9. on 12. on, with, about 1. Smoking is unhealthy, but a lot of people find it difficult to stop. 2. I'm fed up with living in the city - it's too dirty and crowded. 3. I enjoy walking in the garden at weekends. 4. I have decided to stop going out in the evenings so that I can save some money for my holidays. 5. He's an artistic person - very good at writing poetry. 6. They don't like walking, and go everywhere by car. 7. She's going to continue studying for another two years, until her exams. 8. They are thinking of moving house. 9. 'That machine? Oh, it's used for making toasted sandwiches.' 10. They have given up eating meat. 11. We are looking forward to seeing you. 12. Before becoming a teacher, he worked in advertising. Here are the completed sentences: 1. We talked about going to Hoi An for our holiday. 2. I look forward to seeing you again next year. 3. She is tired of working for that company. 4. On opening the front door I walked slowly through it. 5. We got into the house by climbing through a window. 6. Are you interested in joining the school club? 7. He is very keen on swimming at the moment. 8. She is very good at listening to what people say. 9. This is used for cutting metal. 10. I'm tired of coming to the same place every week. 11. She is worried about not getting to the airport in time. 12. The car drove off without stopping. Here are the completed sentences with the gerund form of the verbs in brackets, and a suitable preposition if necessary: 1. Were you successful in seeing the manager? 2. Is Mai fond of swimming? 3. He needs more practice in spelling. 4. There's no use in phoning Mr. Nam. He's not at home now. 5. There is little chance of seeing him today. 6. This book is well worth reading. 7. He was prevented from finishing his work by his illness. 8. They are thinking of moving to the countryside. 9. She has had little experience in teaching. 10. He insisted on helping me with the report. Here are the rewritten sentences starting with a gerund: 1. Keeping fit is made easier by swimming every day. 2. Learning a foreign language takes a long time. 3. More frequent cleaning of the machine will solve your problems. 4. Growing your own food is less expensive. 5. Going by train is cheaper than going by plane. 6. Being in hospital is not pleasant.