Thesis Statement: Our local waterways are severely polluted, and actions must be taken to reduce the runoff that contributes to this pollution.

Which of the following is the best example of a topic sentence for an essay with this thesis?

1) Rain gardens are particularly useful near solid surfaces such as parking lots.

2) Rain gardens are located in 30 percent of the residential parkways in Allentown, Ill.

3) Rain gardens include plants and materials that help absorb water into the ground before it is washed into sewers.

4) Rain gardens are a natural way to reduce storm water runoff that pollutes local waterways