Publication -> Less time for teaching
Hence restrict number of publication,
Restriction -> Les income -> less professor
Possible assumption (Pre thinking)
1. Publication has major share in so called outside income.
A Universities generally receive a large percentage of the royalties from works published by their full-time professors.
Analysis : It talks about universities earning, not professor. It does not matter to professor how much uni earns, Hence Out of scope.
B Most professors do not allow their outside work to infringe on time that should be spent on classroom preparation and teaching.
Analysis : This does not seems to support argument at all. Basis of argument is, Outside work results into less time. This talks entirely opposite.
Wrong option
C Restrictions on outside publishing do not apply to part-time or adjunct professors.
Analysis : It talks about partimers not full time professor. Argument is mainly concerned about full time positions. Can be marked out of scope.
D Publishing is the significant source of outside income for full-time professors.
Analysis : Matches Pre thought assumption : Let's negate, "Publishing is not the significant" Hence restriction won't be big demotivating factor for full time position. Breaks the argument.
E All professors at prestigious universities currently publish more material than is permitted under the new rules.
Analysis : Fact, nice to know. It may happen that not all professor publish more than permitted but 99% publish more than permitted. So negation does not break my argument. Hence cannot be correct.
Answer : Option D