Read this passage. Then choose the question that would best help a reader determine what the passage is about.

One of the most pleasant effects of eating chocolate is the “good feeling” that many people experience after indulging. Chocolate contains more than 300 known chemicals. Scientists have been working on isolating specific chemicals and chemical combinations that may explain some of the pleasurable effects of consuming chocolate.

Caffeine is the most well known of these chemical ingredients, and while it's present in chocolate, it can only be found in small quantities. Theobromine, a weak stimulant, is also present in slightly higher amounts. The combination of these two chemicals (and possibly others) may provide the “lift” that chocolate eaters experience.

Why is chocolate a “feel good” food?

What are the harmful effects of eating chocolate?

What ingredients are used to make chocolate?

It is pretty easy to define the right answer, definitely the first option ( Why is chocolate a “feel good” food?)
is the only question that suits the passage and directly refers to the theme. All the paragraphs represented above are telling the reader only about the advantages of eating chocolate, and according to the introductory sentence ''One of the most pleasant effects of eating chocolate is the “good feeling” that many people experience after indulging'' the first one really makes sense.