instruction:
In this task, you're given an ambiguous question (which can be answered in more than one way). Your task is to write a question that clarifies the given question in such a way that the generated question has one unique answer.
question:
Who sang the song cotton fields back home?
answer:
Who sang the song cotton fields back home in 1940?


question:
When did the voting age change from 21 to 18?
answer:
When did the debate begin to lower the voting age from 21 to 18?


question:
What is the name of the main human character in avatar?
answer:

What is the name of the character who is the main human character in Avatar?