Fill in the gaps with the correct preposition to make the sentences complete.

1. Are you worried ... the threat ... an ecological disaster?
2. The oil-tanker collided ... an iceberg.
3. It's a disaster that people have an unlimited access ... natural resources.
4. The rain which was pouring ... for several days caused the flood in our area.
5. Recycled materials can be turned ... new goods.
6. All people should be familiar ... the concept of the greenhouse effect.
7. Do you know that every flight you take contributes ... global warming?
8. The company insists ... the use of low-energy light bulbs in their offices.
9. The new energy-saving laws apply ... all the citizens.
10. Every person is responsible ... the survival of our planet.
11. Many species of plants and animals are in danger ... becoming extinct.
12. Today's lecture will focus ... ecological problems.