Given a factoid/trivia type question, generate the topic of the question. The topic is the entity the question talks about.

Example Input: Chris Difford and Glenn Tilbrook founded which band in 1974?
Example Output: chris difford

Example Input: Physics. What is the SI unit for amount of substance?
Example Output: amount of substance

Example Input: Which British author and campaigner for women's rights, born in 1880, was a pioneer of birth control?
Example Output:
birth control