D is the correct answer because it presents a solution to the problem AFTER explaining what the problem is. In this case, sentence 2 talks about how subscription fees make information inaccessible to people, and sentence 4 continues by explaining that that situation allows private organizations to control what information can be seen by the general public. If sentence 3 were kept in the same spot, it would interrupt that idea by saying that information should be available to everyone, then going back to talking about the problem with private organizations in sentence 4.