This research investigated the problem of air pollution (cause) ________by vehic

游客2023-09-19  20

问题 This research investigated the problem of air pollution (cause) ________by vehicles in the city of Tripoli, Libya.

选项

答案 caused

解析 空格所填词汇修饰名词air pollution“空气污染”,应用所给提示词的过去分词形式作后置定语,故用caused。
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