第18题: [单项选择]As early as 1637 Ohio made a decision that free, tax supported schools must be established in every town_____40 households or more. A. having B. to have C. to have had D. having had 参考答案:A 答案解析:根据句子结构,空格后的部分是修饰“every town”,作定语讲,应选择分词“having”。