Our local park needs to be cleaned because the litter makes it a less fun place for the community to spend time. People are more more likely to add litter to the park in its current condition, and fewer people use parks that are dirty. Children and adults need a safe place to play and exercise. Therefore, the park needs to be cleaned.

What is the best revision of the last sentence in this concluding paragraph?

Stop littering in the park because it is ruining the environment.
Our local park is a fun place to be, and it helps people meet others in the community.
Help out by joining the park cleanup group, and make a difference in the community.