Answer:
The detail that best supports the idea is D It's great for watering vegetable plants and flowers around your house. I use it to fill my fish tanks, even to wash the car if you want to
Explanation:
There are some keywords in the main idea like water use, easy, inexpensive, effective. It is said that a lot of water is used during the hottest season of the year but it is also mentioned that there are some rains around, then using rainwater can help you reduce your expenses on the water use during those months, it is a good way for all in the economic and environmentally friendly way.