Exercise 2. Fill in: since or for.

David Jones has been working for the same company 1)…. 20 years. He has been a supervisor 2)… 1991 and he quite likes the work, but he has been thinking about changing jobs 3)… he discovered that he has a real talent for garden design. He has been studying garden design part-time 4)… two years and 5)… last month he has been preparing for his final examination. David has been interested in gardening 6)… he was a child and he has known 7) … years that his present job was not the best one for him. He has been much happier 8)… he started the course and 9)… weeks he has been looking forward to the tour that his college has organised. 10)… David started the course, his wife has become interested as well and now they are talking about setting up a business together.