A senior U.S.official acknowledges the clock is ticking on showing the effectiveness of America's multibillion dollar attempt to rebuild Afghanistan.

VOA: standard.2009.09.04

We get used to the ticking of a clock or to noise of traffic but it's actually a very important form of learning because imagine life without it.

我们习惯了钟的滴答声和车来人往的噪音,但这却是一种非常重要的学习形式,我们不妨试想一下无法进行习惯化的情形。

耶鲁公开课 - 心理学导论课程节选

but she has not had the best of luck in the romance department and, with her biological clock ticking away, she has decided the "right guy" may never show up.

VOA: standard.2010.04.30