Title: Railway electrification system.
Question: What is the solution many lines came up with in order to avoid replacing present rolling stock?

Title: Qing dynasty.
Question: What was the name of Xianfeng's concubine?

Title: Anthropology.
Question: Who did a comparative work on a Balinese state?

Title: The Blitz.
Question:
How many bombers hit Plymouth on Hitler's birthday?