Given scientific fact as input, generate the question from this fact such that it can be answered from the input.
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Question: 40 m/s north of the following represents the velocity of a moving object.

Answer: Which of the following represents the velocity of a moving object?

Question: Producing sperm and secreting testosterone are the main functions of male reproductive system system.

Answer: Producing sperm and secreting testosterone are the main functions of what system?

Question: Alkaline earth metals are silvery grey color.

Answer:
Alkaline earth metals are what color?