A. do nothing to keep the balance (平衡)of nature B. try his best to change the balance of nature C. try his best to keep the balance of nature D. do his best to stop the balance of nature 参考答案:C 答案解析:[精解] 概括题。题目问;从文章中,我们知道人类必须怎么样 由于整篇文章主题是讲森林对人类的意义和保护森林。自然答案[C]在意思的表达上,更好的表达了这样的含义。本题答案为[C]。