TASK DEFINITION: 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.
PROBLEM: Who played keyboard on the beatles rooftop concert?

SOLUTION: Billy Preston

PROBLEM: What kind of rose is used to make rose water?

SOLUTION: Rosa × damascena

PROBLEM: Who won the 2017 french open men's singles?

SOLUTION:
Rafael "Rafa" Nadal Parera