图片来源于网络
meaning: If someone is left or kept in the dark about something, they are not informed about it.
意思: 如果某人对某事一无所知，表示别人没有告诉他这件事。
图片来源于网络
-I was kept in the dark about the intervention until a few minutes before it was a reality.
我一直被蒙在鼓里，直到几分钟后它成为现实时，才知道。
3.heavens open
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meaning: When the heavens open, it suddenly starts to rain heavily.
意思:当天空打开的时候，表示突然开始下大雨。
-When we left school, the heavens opened and we were soaked within a few minutes.
-我们离开学校时，突然开始下大雨，几分钟后我们就湿透了。
4.once in a blue moon
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meaning: If something occurs in once in a blue moon, it happens very rarely.
意思:某事很少发生。
