Answer - B - A negative social effect of gentrification in cities would be that increased rents and real estate prices would force out poorer residents.
Key Takeaway: Gentrification is basically the changes that result in an area (usually an urban area) that are the direct result of wealthier people buying homes in poorer communities. Usually, gentrification leads to increases in the community's mean income and decreases in the average family's size. This often leads to an informal eviction of lower-income residents, for whom the strain of newly-raised property taxes, house prices, rents, and more affluent businesses, become increasingly difficult to bear.