Dưới đây là những từ thích hợp để điền vào chỗ trống trong đoạn văn:

26. **too**
27. **is**
28. **too**
29. **that**
30. **to**

Đoạn văn hoàn chỉnh sẽ như sau:

"We are all slowly destroying the earth. The sea and the rivers are **too** dirty to swim in. There **is** so much smoke in the air that it is unhealthy **to live** in many of the world's cities. In one well-known city, for example, the gases **that** cars pollute the air so much that traffic policemen **have** to wear oxygen masks."