The author mentions the "social movement" (Last paragraph) generated by Chicago’s South Side community primarily in order to

A．inform the reader of events that occurred in the meat-packing industry.
B．suggest the history’s limitations by pointing out a situation that the history failed to explain adequately.
C．introduce a new issue designed to elaborate on the good relationship between meatpackers and Chicago's ethnic communities.
D．suggest that the history should have focused more on the relationship between labor movement and healthy industrial communities.