[Answer] Tens of thousands of people are demonstrating in this Czech city in what organizers described as "the biggest protest since the fall of Communism."

Step 1 : Introduction to the question "Tens of thousands of people are demonstrating in this Czech city in what organizers described as "the biggest protest since the fall of Communism.""

...Protesters in Prague are demanding the resignation of Prime Minister Andrej Babis, accused of fraud and collaborating with the Communist-era secret police, and his justice secretary Marie Benesova.