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]: When does the rpdr season 9 finale air?
[A]: June 23, 2017


[Q]: The proof of having paid the road toll for swiss highways is called?
[A]: Vignette


[Q]: Who taught that governments should be ruled by philosopher-kings?
[A]:
Plato