The communist North called off reunions in response to what it considers South Korean President Lee Myung Bak's hard-line policy.

VOA: standard.2009.08.26

And now the bell--When--You start off with the unconditioned stimulus, unconditioned response.

开始时呈现无条件刺激，会出现无条件反应。

耶鲁公开课 - 心理学导论课程节选