In this task, you're given an open-domain question. Your task is to provide an answer to the given question. There is only one unique answer for each question. Your answer should be short, and refer to an entity, date, number, etc. Do not put your answer in the context of a sentence.

[Q]: Who wrote the strange case of dr jekyll and mr hyde?
[A]: Robert Louis Stevenson


[Q]: How many episodes are in season 4 of agents of shield?
[A]: 22


[Q]: What was the first underground line in london?
[A]:
Metropolitan Railway