◎ 题干
—Our environment is getting worse than before.
—You're right. But people have done more and more
    useful things to protect (保护) the earth since Earth Day _____.
[     ]
A. is started
B. was started
C. has started
◎ 答案
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◎ 解析
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◎ 知识点
    根据魔方格专家分析,试题“—Our environment is getting worse than before. —You're right. But people have done more and moreuseful things to protect (保护) the earth since Earth Day ____…”主要考查了你对  【被动语态】【一般过去时】  等知识点的理解和应用能力。关于这些知识点的“档案”,你可以点击相应的链接进行查看和学习。