Official Explanation
1. What distinguishes the commentaries on the Jiuzhang Suanshu from almost all other works of Chinese mathematical history is that the authors of the former
Difficulty Level: Medium
Explanation
Most Chinese mathematical works stated results only, without the proofs justifying the results. The commentaries on the Jiuzhang Suanshu are different in that they contain both the results and the proofs. In other words, they provide "explicit proofs for the mathematical results presented", which is precisely what choice (D), the credited answer, says.
The majority of Chinese mathematical works did not include proofs, but they all said what was true. Both the commentaries on the Jiuzhang Suanshu and the other works "made clear exactly what theorems are true", so this does not distinguish them. Choice (A) is not correct.
The passage talks about "justification" in terms of the logical justification a mathematical proof implies. Nowhere does it discuss people justifying themselves. Choice (B) is not correct.
Choice (C) sounds awfully fancy, but it's not 100% clear what it even means. The authors of the commentaries on the Jiuzhang Suanshu "did not fully disclose all the results in the fields discussed"(??) Well, the only "field discussed" is mathematics. The verb "disclosed" is particularly odd, because it implies that someone was keeping secrets by withholding information, something not mentioned in the passage at all. As stated in answer choice (A), all Chinese mathematical works stated "results", i.e. what was true; only the commentaries on the Jiuzhang Suanshu also showed the proofs, i.e. why things were true. In that sense, the commentaries on the Jiuzhang Suanshu showed (disclosed?) more than the other works. Insofar as this choice says anything meaningful, it contradicts the passage. Don't be fooled by fancy wording. Choice (C) is not correct.
We know the commentaries on the Jiuzhang Suanshu "had influence over a large portion of Chinese history" because they "served as a reference for it over a long period of [Chinese mathematical] history." Does this make the commentaries on the Jiuzhang Suanshu different from other works of Chinese mathematics? Do we have the grounds, based on the passage, to conclude that absolutely no other work of Chinese mathematics had any influence over the course of China's long history? Hmm. That seems like a stretch. The passage only talks about the influence of the commentaries on the Jiuzhang Suanshu, and says zilch about whether other works had a long influence. We just don't know. Choice (E) is not correct.
Answer: D