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Mary Simms (outdoor advertising rep): "Billboards are the basis of our business. If they are torn down, our ability to earn a living will be severely damaged.
Jack Jordan (local merchant): "The basis of our business is an attractive community..."
When Mary said "our", she meant her advertising business.
When Jack said "our", he meant the town/community.
Hence (C) is the correct answer.
Admin note: edited title; please use the format of "PT#.S#.Q# - [brief description]"