B. Because Stephano wants to be Caliban’s master, not just king of the island.
Explanation:
The fact that Caliban wants Stephano to be king shows his faulty reasoning. Caliban does not realize the extent of Stephano's ambitions. Caliban's main desire is to rid himself of Prospero, who is a tyrannical master. However, he has not fully realized that by becoming king of the island, Stephano would also become Caliban's master. Therefore, Caliban would not gain his freedom, but only change his master.
