摘要：781] As middle school students, we the police to keep order. [译文] 作为中学生.我们过去常常帮助警察维持交通秩序. A. are used to help B. used to helping C. used to help D. used to be helped [答案及简析] C. used to do sth. 过去常常做-,be used to doing sth.习惯语做-.

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