When you are asked to identify an ADDITIONAL PREMISE that would make the argument more logically valid, you must first identify the logical gap in the argument.

First, identify the conclusion of the argument and the premises given that support it. Then think: what information is missing that would allow that conclusion to follow from those premises? Or think of the flip side: what would make the conclusion NOT true, even given those premises?

Then as you're going through the answer choices, think: does this HAVE to be true? If it weren't true, would that destroy the argument?

Premises:
- most universities retain the royalties from faculty members' inventions
- the faculty members retain the royalties from books and articles they write.

Conclusion:
- faculty members should retain the royalties from the educational computer software they develop.

Missing information:
- there must be some reason to believe that educational software is more like books/articles than like inventions.

(A) Royalties from inventions are higher than royalties from educational software programs.
Irrelevant. We need to know how to categorize software. There's no reason to believe that $$ is relevant to the categorization.

(B) Faculty members are more likely to produce educational software programs than inventions.
Irrelevant to the categorization.

(C) Inventions bring more prestige to universities than do books and articles.
This doesn't tell us anything about software. Irrelevant.

(D) In the experience of most universities, educational software programs are more marketable than are books and articles.
Marketability has nothing to do with how these things are categorized for royalties.

(E) In terms of the criteria used to award royalties, educational software programs are more nearly comparable to books and articles than to inventions.
This is exactly what the argument was originally missing. If this were NOT true - if software was more comparable to inventions - then the argument would make no sense.

The answer is E.