(Test) The U.N.Secretary-General says he is "optimistic" a climate-change agreement can be reached in Copenhagen that will include specific recommendations on key elements that will take effect immediately.

VOA: standard.2009.12.09

And again, there'll be key elements that run in cycles and understanding those can be extremely important in understanding how cellular function works.

同样地，在循环中也会有,一些关键的要素,研究这些对于理解细胞的,运作机制是极其重要的。

麻省理工公开课 - 热力学与动力学课程节选

The thesis of 3.091, and this is where the chemistry comes in, is that electronic structure of the elements holds the key to the understanding, not just the chemical bonding, but the long range atomic order.

这是这门课的论点，这是化学的研究点，也就是元素的电子结构,那即是理解的关键，不只是化学键，还有长程的原子排序。

麻省理工公开课 - 固态化学导论课程节选

They make sure key elements in the plot are there.

VOA: standard.2010.05.07

The president has said on numerous occasions that the key to combating al-Qaida and Taliban advances is a regional approach that includes three elements: military action,diplomacy, and support for development.

VOA: standard.2009.03.26