Explanation
Correct answer: C.
Choice C is the best answer. The text tells us that because of the copyright, adapting Sherlock Holmes stories used to be expensive and difficult. This suggests that after the copyright ends, it will be less expensive and less difficult to adapt these stories.
Why the other choices are wrong
Choice A
Choice A is incorrect. This inference isn’t supported. The text never suggests that the copyright ending will make Sherlock Holmes stories harder to find. Instead, it suggests that adaptations of these stories will be easier and less expensive to make.
Choice B
Choice B is incorrect. This inference isn’t supported. The text never discusses people’s interest in detective stories, so there is no basis to make this inference.
Choice D
Choice D is incorrect. This inference isn’t supported. The text never suggests that copyright fees from the past are returned after a copyright ends, so there is no basis to make this inference.