Which of the following best reflects the materialist's response to the problem of mind-body interaction ('mind/body problem')?
1) The mind and body interact with each other by way of a miracle
2) The mind and body interact with each other through waves of communication through space (like radio waves)
3) The mind and body do not interact with each other, even though they are two fundamentally different kinds of substances
4) There is no problem of mind-body interaction because the mind is a physical thing just like the body.
5) There is no problem of mind-body interaction because nonphysical and physical things interact all the time in the world.