In a large saucepan cook carrots, celery, and onion in hot olive oil about 5 minutes or until crisp-tender. Stir in water, cabbage, lentils, tomato puree, sugar, salt, oregano, and pepper. Bring to boiling; reduce heat. Cover and simmer for 45 minutes or until lentils are very soft. Ladle into bowls. Makes 5 main-dish servings.