Critical Reasoning

Community activist: If Morganville wants to keep its central shopping district healthy, it should prevent the opening of a huge SaveAll discount department store on the outskirts of Morganville. Records from other small towns show that whenever SaveAll has opened a store outside the central shopping district of a small town, within five years the town has experienced the bankruptcies of more than a quarter of the stores in the shopping district.
The answer to which of the following would be most useful for evaluating the community activist’s reasoning?
A. Have community activists in other towns successfully campaigned against the opening of a SaveAll store on the outskirts of their towns?
B. Do a large percentage of the residents of Morganville currently do almost all of their shopping at stores in Morganville?
C. In towns with healthy central shopping districts, what proportion of the stores in those districts suffer bankruptcy during a typical five-year period?
D. What proportion of the employees at the SaveAll store on the outskirts of Morganville will be drawn form Morganville?
E. Do newly opened SaveAll stores ever lose money during their first five years of operation?

IMO - B-->Depending the % of shoppers, impact on the stores at M can be determined.

But the answer seems to be C, can anyone explain why? Tx much