looked at things like where should they locate waste water treatment facilities because of the impacts of climate change, what risks are likely to occur to their subway system because it's underground and already requires enormous pumping of water during certain large rainfall events."

VOA: standard.2010.06.14

And what this is in a very general sense is the learning of an association between one stimulus and another stimulus, where stimulus is a technical term meaning events in the environment like a certain smell or sound or sight.

一般来说,经典条件作用是指在一个刺激,和另一个刺激之间形成联结，这里的刺激是一个专业术语,意思是环境中出现的事件,比如某种味道，声音或景观。

耶鲁公开课 - 心理学导论课程节选

Use "When" whenever you want to ask about the timing of a certain event or series of events.

当你想要询问一个或一系列事件的具体时间时，你可以用“When”句型。

When 课堂 - SpeakingMax英语口语达人