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 "In the 20th century, Greek composers have had a significant impact on the development of avant garde and modern classical music, with figures such as Iannis Xenakis, Nikos Skalkottas, and Dimitri Mitropoulos achieving international prominence.". Is that enough to answer the question?