どなた（どなた）— who (polite)
どなた が 先生 です か。
Who is the teacher?
どなたどなた
who (polite)
どなた
accent [1]In detail
Words
どなたdonatawho (polite)
がga(subject marker)
先生senseiteacher
ですdesu(polite sentence ending)
かka(question marker)
どなた is a polite alternative to 誰. Use it when you want to show respect toward the person you are asking about.
Coco-sensei