1. Although Lan can't play the piano, she can sing very well.
2. If we use the car all the time, we will make the air dirty.
3. No river in the world is longer than the Nile river.
4. In the future,home robots will do all our housework.
5. It's the first time I have read a more romatic story.
6. The doctor says that unless my father continues to smoke, he won't be ill.