Final answer:
The main scientific objection to the psychic's claim of reading minds on the planet Zipton is that it exceeds the speed of light communication.
Step-by-step explanation:
The main scientific objection to the psychic's claim of reading minds on the planet Zipton, millions of light years away, is that it c) Exceeds the speed of light communication. According to the laws of physics, communication cannot occur faster than the speed of light. Light itself, traveling at the fastest speed in the universe, takes around 4 years to reach the nearest star. Therefore, any claim of mind-reading from such a distant location would violate the fundamental principle of communication speed.