What to put for primary ethnicity

Tess • Nari Lyn 11/13/17•Emma Rose 3/17/19•Pierce James 9/28/20•Willow Grace 3/22/22

Sorry if this is a stupid question, but I’m registering my daughter for pre-k and it’s asking what her primary ethnicity is. She is half Korean and half caucasian. I’m not sure what to put, honestly if you looked at her you wouldn’t think she was half caucasian. I can only choose one so I’m not sure