第17题: [单项选择] It is naive to expect that any society can resolve all the social problems it is faced with______. A. for long B. in and out C. once for all D. by nature 参考答案:C 答案解析:once for all是“一劳永逸”。A.for long是“长久”;B.in and out是“里外”;D.by nature是“本质上”。