单选题 More than forty thousand readers told us that they looked for in close friendships, what they expected__21__friends, what they were willing to give in__22__, and how satisfied they were__23__the quality of their friendships. The__24__give little comfort to social critics. Friendship__25__to be a unique form of__26__bonding. Unlike marriage or the ties that__27__parents and children, it is not defined or regulated by__28__. Unlike other social roles that we are expected to__29__ —as citizens, employees, members of professional societies and __30__organizations—it has its own principle, which is to promote__31__of warmth, trust, love, and affection__32__two people. The survey on friendship appeared in the March__33__of Psychology Today. The findings__34__ that issues of trust and betrayal(背叛) are__35__to friendship. They also suggest that our readers do not__36__for friends only among those who are__37__like them, but find many__38__differ in race, religion, and ethnic(种族的)background. Arguably the most important__39__ that emerges from the data, __40__, is not something that we found—but what we did not.