I would say that the option that best identifies the theme of the text is <em>B: The most beautiful moments of life are brief.</em>
Explanation:
I chose the second option because I believe that what the author is trying to say is that there are golden moments, perfect periods of time, that suddenly arrive and, also, suddenly disappear. In this text, he is expressing this by using metaphor, comparing those beautiful and brief moments of joy and happiness with the moment in which nature gives us her first "<em>green</em>", her flower;<em> </em><em><u>that magical moment that only lingers for a little while</u></em>. So, the author is comparing those magical and brief moments where nature give us flowers with our personal and unique brief moments that also are brief and magical.
