I know that it was once in a blue moon that he would fail an important exam. So I don't think that he will turn grey because of this.

我知道他很少在重要的考试中失手，因此我不认为他会因此而愁白了头发。

youdao

I know that it was once in a blue moon that he would fail an important exam. So I don't think that he will turn grey because of this.

我知道他很少在重要的考试中失手，因此我不认为他会因此而愁白了头发。

youdao