Every possible means(use)______ to prevent the air pollution, but the sky is sti

游客2023-10-06 11

问题 Every possible means(use)______ to prevent the air pollution, but the sky is still not clear.

选项

答案 has been used

解析本题考查语法。根据but可知这是两个分句，所以前边应该用谓语构成一个完整的句子，而且根据句意应该是被动语态，并且是“已经被使用了”，所以应该用现在完成时的被动语态，其构成是：has/have+been+及物动词的过去分词。

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