Determine the topic of the question. Question: "what is in milk?" Topic:
Ans: Milk

Determine the topic of the question. Question: "who plays as big bird?" Topic:
Ans: Big Bird

Determine the topic of the question. Question: "what is prince williams last name?" Topic:
Ans: Prince William, Duke of Cambridge

Determine the topic of the question. Question: "how long did the roman empire last?" Topic:
Ans: Roman Empire