单选题 17.As early as 1647, Ohio made a decision that free, tax-supported schools must be established in every town______50 households or more.

【正确答案】 A

【答案解析】正确答案为A，在这里having 50 households or more作定语修饰every town。由于此处不强调have的非谓语动词所表示的动作和谓语动词establish所表示的动作哪个先哪个后，因此其他三个选项错误。