The key to a successful project is to manage change by clearly defining the requirements and to adapt them as needed over the solution development cycle.

成功项目的关键是通过清晰地定义需求来管理变化，并在解决方案开发周期中根据需求适应变化。

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Though methane is not as abundant as carbon dioxide, it is twenty times more potent and scientists believe that over the eons it has played a key role in spurring climate change.

虽然甲烷不如二氧化碳量大，但（作为温室气体）其强度是二氧化碳的20多倍，科学家们认为，长久以来它一直是推动气候变化的关键角色。

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One key change in global public health over this time has been the rise of non-state actors.

FORBES: The Fight to End Pandemics

But, according to the United States, the only change in their low-key military relations is that Paraguay has approved several (small-scale) American exercises over the next 18 months all at once, rather than singly.

ECONOMIST: A flirtation unsettles the neighbours