What should a girl say to a male teacher if she wants to use his photo as a WeChat avatar?

A girl wants to use a photo of a male teacher as a WeChat avatar. What should she say to the male teacher? If a girl wants to use a photo of a male teacher as a WeChat avatar, she must get the consent of the male teacher. She can tell the teacher that I admire you very much. I want to use your photo as a WeChat avatar, and I can't use it until I get permission.