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:
Which unit is used to measure mass in the metric system?
answer:
kilogramme


question:
Voice of optimus prime dark of the moon?
answer:
Peter Claver Cullen


question:
Who discovered the direction of magnetic field lines?
answer:

Hans Christian Ørsted