3 1. These ancient buildings are not open to the public this month because they are under repair. 2. Fitness is a key/basic/major element in living a happy life, but many people fail to take good care of it. 3. The UN plays a major/leading/significant role in promoting understanding in the international community. 4. Politicians tend to make big promises during an election campaign/in their campaign speeches . 5. The champion boxer fought bravely to defend his title, but was finally laid low by a knockout blow. 6. It is important for parents to train their baby not to scatter their toys everywhere. 7. School children are no longer encouraged to hang around with friends after school. 8. It is natural for a foreigner to speak the language with a trace of an accent. 9. PM 2.5 are fine particles suspended in the air that pose hazards to the health of humans. 10. The two countries are in dispute over the boundaries of their coastal waters.