Sometimes people get caught in a "downward spiral," a case in which something leads to a result which in turn leads to more of the original thing, bringing on more of the result. As the process continues, the result continually gets worse and worse. An example is when people turn to binge eating when depressed, which causes them to put on weight and feel unhealthy, which then makes them more depressed, leading to more overeating, and so on. The author is mainly concerned with:_______a. Convincing people not to overeat. b. Explaining the process of the "downward spiral." c. Showing how overeating can lead to depression. d. Showing how some processes lead to surprising results.