Question: What is the question to: "Black Friday is the day following Thanksgiving Day in the United States , often regarded as the beginning of the Christmas shopping season."? The topic is Black Friday (shopping).
Answer: "when does black friday start for christmas?"

Question: What is the question to: "A gristmill (also: grist mill, corn mill or flour mill) grinds grain into flour ."? The topic is Gristmill.
Answer: "what is grist mill stone?"

Question: What is the question to: "Copper is a chemical element with the symbol Cu (from ) and atomic number 29."? The topic is Copper.
Answer:
"what is cu the element?"