The correct answer is (E).
(E) Strengthen
Step 1: Identify the Question Type
While most questions on the LSAT that ask you to fill in the blank are Inference questions (essentially asking for the logical conclusion), this one asks you to fill in the blank with something that will "strongly [support]" the argument. This means you need to fill in a piece of evidence that will strengthen the argument, making this a Strengthen question.
Step 2: Untangle the Stimulus
The author starts by stating the original function and purpose of copyrights: They gave authors a monetary incentive to circulate their ideas. With the Keyword "however," the author introduces a contrast, concluding that copyright sometimes goes beyond this purpose. The blank at the end must be filled by a missing piece of evidence (indicated by the Keyword "since") that would support that conclusion.
Step 3: Make a Prediction
At this point, the author has defined the original role of copyright (a financial incentive for authors to circulate ideas) and concluded that copyright sometimes exceeds this role. What's missing is an example or explanation of how copyright sometimes exceeds its original role. The correct answer will state a way in which copyright is sometimes not limited to financially rewarding authors.
Step 4: Evaluate the Answer Choices
(E) does the job. After an author dies, financial incentives for that author would become immaterial. If copyrights still hold past that time, then they must be surpassing the original purpose, as the present author concludes.
(A) offers an alternative to copyright for the circulation of ideas, but doesn't discuss whether or not copyrights sometimes go beyond the original intentions.
(B) suggests that authors don't need the financial incentive copyright offers, but again, the answer choice doesn't address the argument's assertion that copyrights exceed the original purpose behind them.
(C) is irrelevant, since difficulty in finding a publisher has no effect on the purpose of copyrights.
(D) is Outside the Scope. This is an argument about the goals of copyright protection, not its efficacy. If anything, a lack of enforceability probably reduces the purposes a law can reasonably be said to have. In any case, this choice doesn't make the argument any stronger.
