Which phenomenon may explain why some people want to join a fraternity or sorority badly enough that they will endure weeks of humiliation and physical discomfort to gain membership? cognitive dissonance justification of effort insufficient justification conditioning?

The correct answer is justification of effort.
Individuals who want to join a fraternity or sorority go through various difficult and often embarrassing trials in order to gain membership. They need to justify why they tried so hard, which falls under the category of justification of effort, a theory proposed by Leon Festinger. Often their justification is much greater than the actual results. 

The correct answer is justification of effort 

Justification of effort refers to the phenomenon in which individuals view a goal or accomplishment as more worthwhile and fulfilling if they have to put in great efforts, make sacrifices and work hard in order to achieve it. In this instance by undergoing humiliation, discomfort and compromises, people who are accepted into sororities or fraternities can find being part of them more rewarding.