问题
选择题
| _____ environmental damage is done, it takes many years for the ecosystem (生态系统) to recover. |
| A. Even if B. If only C. While D. Once |
答案
答案：D
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| _____ environmental damage is done, it takes many years for the ecosystem (生态系统) to recover. |
| A. Even if B. If only C. While D. Once |
答案：D