害虫通常以特定的树种为目标，一旦形成，它们通常会成为生态系统的永久组成部分。
Pests often target specific tree species and, if they become established, they usually remain as permanent components of the ecosystem.
中国官方媒体报告说，中国的最终目标是建造一个永久的空间实验室，和一个大型太空工程系统。
Official Chinese media report the country's ultimate goal is to build a permanent space laboratory and a larger-scale space engineering system.
任何地方的任何挑战都不得危及我们的目标，这就是消灭一种非常可怕的疾病，使世界得到永久改善。
No challenge anywhere can be allowed to jeopardize the goal of permanently improving the world by driving out a truly awful disease.
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