【单选题】

According to the passage, what kind of people are rare
A．Those who don't emphasize bookish excellence in their pursuit of happiness.

B．Those who are aware of difficulties in life but know how to avoid unhappiness.
C．Those who measure happiness by an absence of problems but seldom suffer from N. B. D. 's.
D．Those who are able to secure happiness though having to struggle against trying circumstances.