From the expressions on their faces, I realized the gravity of the situation.

从他们的脸部表情我晓悟到事情的严重性。

《新英汉大辞典》

Although I could not understand everything the characters said, their body language and the expressions on their faces helped me to get the meaning.

尽管我听不懂各个角色说的所有台词，但他们的肢体语言和面部表情帮助我理解意思。

youdao

From the changing expressions on speakers' faces and the tones of their voices, they can tell lies from truths.

从讲话者表情上的变化和说话时的语调，他们可以看出这些人是否在说假话。

youdao

The expressions on their faces are still a source of horror.

NEWYORKER: Naima

Except for the unhappy expressions on their faces, they looked like they had settled in for a tailgate party.

CNN: Why a pundit wrote a novel