由于这些数据有时相互矛盾，而且其机制也不时发生明显的变化，这些研究变得复杂起来。

The studies are complicated by the fact that the data are sometimes contradictory and the mechanisms apparently change from time to time.

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无论你是人际关系网的高手还是新人，总会时不时遇到一些挑战，而有时我们就需要依靠其他人的鼓励和帮助来渡过难关。

Whether you're a master networker or you're new to networking, we all face challenging situations at times, and sometimes we need to rely on the help and encouragement of others.

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然而，有时候项目经理并不知道小的范围变更时不时会被追加进来。

However, sometimes the project manager doesn't recognize the small scope changes that get added over time.

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