instruction:
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.
question:
What's the name for earth's supply of water?
answer:
hydrosphere


question:
When was the bill of rights last amended?
answer:
May 5, 1992


question:
What era relates to the old stone age from around 3 million years ago to 9000 bc?
answer:

Palaeolithic