This statement can be considered the theme and not ta plot summary because (D) It relates to universal idea about life.
We also know that the theme is the general issue that deals with a story (love, trust, jealousy). It is generally a phrase that synthesizes or encompasses the entire text, a very brief exposition of the central idea of the writing around which the meaning of the text is organized and which gives universal meaning to the specific data or events presented by the text. Instead the plot is the sequence of events in the order in which they appear in the story.
Author Joshua J. Marine has a famous quote on this: “Challenges are what make life interesting and overcoming them is what makes life meaningful.” ... But any way you look at it, it ensures that life is interesting and fulfilling.