I want to know the answer to the following question:
Who is one of the notable Greek opera singers in the 20th century?
All the background I'm provided with is that "Notable Greek opera singers and classical musicians of the 20th and 21st century include Maria Callas, Nana Mouskouri, Mario Frangoulis, Leonidas Kavakos, Dimitris Sgouros and others.". Is that enough to answer the question?
Answer: yes