Who or Whom?
Your choice!
Who
Exemple : ‘’Who has finished their meal?’’
As relative pronouns "who" and "whom" can be used interchangeably in order to link clauses together. The use of "whom" denotes a much higher register. In questions "who" is used to represent a subject.
Whom
Exemple : ‘’To whom would you like to speak?’’
In questions "whom" is used to represent an object and is also used after prepositions. "Whom" is always used after quantifiers such as "most of", "all of", and "few of."