Ricky tried to dye his hair black but left the dye on too long; clumps of his hair fell out completely, leaving weird bald patches on his scalp. the kids at school snickered at him, ignored him, and avoided him at lunchtime for a couple of weeks. after that, though, everyone forgot about it. thus ricky was subjected to a short-term bout of

The correct answer is social ostracism.
Ricky was ostracized from the society, which means that he was basically rejected by the people around him based on something he did or the way he looked. In his case, everyone exiled him from the 'school society' because of his weird bald patches on the scalp, but once they were gone, he was readmitted into the society. 

Clean air provides nitrogen