An astronaut standing on the surface of the moon throws a ball upwards. The ball would

This is the same case that would have happened if the ball was thrown upwards from the surface of the Earth. The ball would go upwards first and then come back to the surface because of the action of the gravity. In this case, the ball is thrown from the surface of the moon where gravity is less than that on the Earth, but gravity exists and because of its pulling action, the ball will hit the surface of the Moon.