《2025年小学教材全解六年级英语上册沪教牛津版三起》

Complete the notes.
• The smoke in the street comes from the cars/buses, buses/cars and a factory.
• The air is dirty in the street. The air is fresh/clean and clean/fresh in the park. There are a lot of trees in it.
• Trees keep the air clean.

答案： cars/buses, buses/cars, factory, dirty, fresh/clean, clean/fresh, trees, clean