不幸的是，尽管不希望长期存留，然而书页至今仍牢牢地粘在一起。
Unfortunately, leaves of books continue to stick fast even when they are no longer wanted.
在植物把它们播撒四方之后，它们可以长期存留在湖底的淤泥里或者或化石中。
After plants spread theirs far and wide it can be preserved in lakebeds or fossilized in soil.
虽然氯联苯没有很强的直接制毒性，但是它们能长期存留在环境中，并积存在人体组织里。
Although PCBs have a low immediate toxicity, they are very persistent in the environment and accumulate in tissues over time.
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