out of ·phrase (IDIOM)
Definition: If something happens out of the blue, it is completely unexpected. Level: C1
有一天，她毫无预兆地宣布她要离开。
One day, ___out ___of ___the ___blue, she announced that she was leaving.
当我意外收到你的来信时，我高兴极了。
I was extremely happy when I received your letter ___out ___of ___the ___blue.
这个工作机会来得非常意外，彻底改变了他的职业规划。
The job offer came ___out ___of ___the ___blue, completely changing his career plans.