风一向多变，因此它永远比不上廉价又脏兮兮的煤，后者产出了美国半数电力。
Wind is inherently variable, so it can never compete with the cheap and dirty coal that generates half of America's electricity.
童年期向青春期的转变阶段是发育的关键时期，生理、认知及社交等方面随之发生许多变化。
The transition into puberty is a critical developmental period, associated with many biological, cognitive and social changes.
在动态多变的市场环境下，供应链需要以最小的成本、最短的时间向顾客传递更多的价值。
In the dynamic and changeful market environment, a supply chain should use the least cost to transfer the most value to the customers in the shortest time.
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