The passage is primarily concerned with
Incorrect.
[[snippet]]This answer choice is too narrow. Our initial reading shows that the passage brings Dietsch's opinion that the graduate tax should justly be imposed - not on whether it would reach its goal. If you read too much into the second paragraph, you will find that it also deals with the efficacy (=effectiveness) of a graduate tax by telling us it will get rid of tuition fees - but that's just a small part of what the passage does, not the primary concern. Even so, the second paragraph merely states that a graduate tax will be effective, but does not evaluate (=judge) its efficacy.
Incorrect.
[[snippet]]This answer choice is too specific. The passage mentions only a single shortcoming in the first paragraph (that government funding violates a principle of justice), but does not just analyze it - it actually proposes an alternative. The correct answer to a Main Idea question must be general.
Incorrect.
[[snippet]]This answer choice is too specific. Sticking to the Initial Reading, we can see that the passage does not defend an abstract principle (the beneficiary should pay), which is mentioned at the end of the first paragraph. That principle is taken as a given which does not need defending, and the passage's main concern is to justify a concrete method (a graduate tax), which embodies this just principle.
Incorrect.
[[snippet]]Although the passage enumerates (=lists) alternate funding methods in first paragraph, it is not overall concerned with describing them. This is just one thing the passage does - not the main concern.
Well done!
[[snippet]]According to the Initial Reading passage is concerned with justifying (=making a case for) the shift (=change) from funding via the general tax system to funding by means of a graduate tax. The first sentence of the second paragraph explains one of the advantages of such a shift (tuition-free education).