David was a young man who worked in an office in a big city. His hobby was fishing, but he didn't often get a chance to practise it. Then one summer he decided to have a holiday in a beautiful place in the mountains where here were a lot of streams. 'I ought to be able to have some good fishing there,' he said to himself. The first morning after he arrived, he walked to the nearest stream with his fishing-rod. He aw an old man standing beside the water, so he asked him whether it was a private(私人的) stream. The old man answered it was not, so David then said to him, 'Well, then it won't be a crime(犯罪) if I catch some fish here, will it?' 'Oh, no,' answered the old man. 'It won't be a crime, but it will certainly be a miracle(奇迹)。' David was ______ fishing.