Complete the sentences below with the correct reference word (it, they, this or these).

1. Having a good job brings happiness to many people because feel that their life is important.

2. Some companies contribute to polluting the environment. is a problem that governments should focus on.

3. Technological advances have helped in medicine, communication and travel. improvements have made a big difference to our lives.

4. Happiness has different meanings for people but is something that is important for everyone.

5. In winter, storms can cause serious damage to shops, offices and houses. Engineers should make buildings stronger.

6. The mountain climbers reached the summit after three weeks. were happy but exhausted.