[译] 见到母亲时，我激动得禁不住哭了起来。
[误] The moment when I saw my mother, I could not help crying with excitement.

[正] The moment I saw my mother, I could not help crying with excitement.
[注] moment 与定冠词连用可以用来引导状语从句。但在 the moment 的后面不能跟关系副词 when，只能跟关系代词 that，而 that 又常常省略，所以在使用中见到的多是在 moment 后直接跟从句。