I want to know the answer to the following question:
What notable political union of the 20th century covered most South Slavs?
All the background I'm provided with is that "In the 19th century, Pan-Slavism developed as a movement among intellectuals, scholars, and poets, but it rarely influenced practical politics and did not find support in some nations that had Slavic origins.". Is that enough to answer the question?
Answer: no