In the natural state of the atmosphere, free-falling bodies are disturbed by air resistance. To eliminate this interference, a vacuum environment must be created. In the era of Galileo, people could not create a vacuum environment by technical means. Therefore, Galileo The factor of air resistance can only be put aside in thinking, and the motion of a falling body in a vacuum is conceived, so that the law of free-falling body is reached, which overturns Aristotle's conclusion about the falling body. For Galileo's law of free fall to be true, which of the following must be premised? ["People at the time we're able to conduct the same thought experiments.", "Galileo's thought experiment conforms to the laws of movement in a vacuum.", 'Galileo validated by realistic experiments at the Leaning Tower of Pisa.', 'Galileo envisions various possibilities.']