【答案解析】文章第二段的开头说：The investigators found survey participants by randomly dialing New York City phone numbers and screened potential respondents for Manhattan residents living in areas close to the World Trade Center．研究人员先是随机地抽取纽约的电话号码，然后只挑选了那些曼哈顿岛上，住所离世界贸易中心比较近的居民。所以C为答案。