1. The sites shield themselves from search engines, so they do not pop up in response to online searches for the brands they offer.
这些网站避开了搜索引擎，所以若在线搜索他们所卖的品牌时，他们的网站是不会出现的。
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2. As noted above, indifferent relationships may not always be the most helpful approach in resolving some of the issues that popup at work.
如上所述，在解决工作中出现的一些问题时，冷淡的关系并不总是最有用的方法。
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3. The same narrative units—gathering armies, heroic shields, challenges between rivals—pop up again and again, only with different characters and different circumstances.
军队集结、英勇抵抗、对手间的争斗，此类叙事单元不断重复出现，只有角色和场景发生变化。
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4. Colds mutate even while they're infecting you, and new strains popup so often that by the time drug-makers create a vaccine against one variation, the serum is already out of date.
