Answer:
C. It explains one way rain barrels benefit you, and one way rain barrels benefit plants.
You can look at the words in front and behind it, because they refer to this big word. You may find a synonym of the word or a close reference. So for example in this sentence: I was excited and ambitious to learn about cars today. So this is a easy example. You can use exited to define ambitious if you dont know what ambitious means.
To be non-biased, have thorough research habits, a good work ethic, to produce the story as closely to the true events as possible (no filler or otherwise distracting language to take attention away from the topic)