To raise one's eyebrows' indicates:

To raise one’s eyebrows (Phrase/Idiom)
English Meaning: to (lift one’s eyebrows in order to) show surprise.
Example Sentence:
- An intriguing item on the news pages caused me to raise an eyebrow over my morning coffee. 
- He raised his eyebrows over some of the suggestions. 
- He was looking at her with his eyebrows raised questioningly. 

Source: Cambridge Dictionary