If B doesn't seem obvious, you can use the process of elimination. "The History of Sewers" would never be a title for an article telling you that water is good for you. An article titled "The Water Cycle" would just go in depth about the water cycle. I don't even know what water fights could be used for. "Eight Glasses a Day Keep the Doctor Away" is a saying many people know, and it shows that drinking water can have health benefits.
