Combine the sentences using relative clauses.

1. Plastic takes hundreds of years to decompose in the ground. This explains why it is harmful to the environment.

→ Plastic takes hundreds of years to decompose in the ground, _____________________.

2. Public transport does not pollute the air as much as private vehicles. That's why more people should consider using it.

→ Public transport does not pollute the air as much as private vehicles, ______________.

3. All students work very hard to help clean up the school. The teacher encourages this.

→ All students work very hard to help clean up the school, ________________________.