Answer:
c.) I made my own rain barrel but you can buy them pretty cheaply now.
Step-by-step explanation:
This is the choice that best represents a supporting detail for this main idea. The main idea of the passage is that it is possible for a community to save money. Option C is the one that best addresses this concern, by stating that a rain barrel can be bought pretty cheaply. Although the other options mention the benefits of barrels, they do not address the economic benefits directly.