B). It emphasizes how much people prefer nature over urban settings.
Explanation:
The chapter titled 'Scientists Reveal Three Keys to Happiness' primarily discusses that <u>how nature influences people</u>. The author proves that 'some specific environments bring out the best in people' which is justified by the illustration provided in paragraph 9. It proves that the pictures displaying scenes of nature were always preferred over the 'urban scenes' despite the quality of latter was much advanced as they were clicked by professional photographers. Thus, <u>it substantiates the claim that nature always rules that gateway for people's happiness. </u>Therefore, <u>option B</u> is the correct answer.
