他沉下脸来，装出一副严厉的样子。

He frowned with mock severity.

《牛津词典》

他们无法动怒似乎削弱了他们的能力，让他们明白为什么咄咄逼人的电话推销员或没得到生日祝愿可能会让一个人沉下脸来。

Their inability to scowl seemed to impair their ability to see why pushy telemarketers or a lack of birthday wishes might make one's face fall.

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当她听到这个坏消息时，她气得沉下脸来。

Her face darkened with anger when she heard the bad news.

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