Read the following passage and questions, then choose the right answer from options, the answer should be one of A, B, C, D.

<passage>:
Open Access: Casualties Will a general shift to OA leave casualties? For example, will rising levels of green OA trigger cancellations of toll-access journals? This question matters for those publishers (not all publishers) who fear the answer is yes and for those activists (not all activists) who hope the answer is yes. So far, unfortunately, it doesn’t have a simple yes-or-no answer, and most discussions replace evidence with fearful or hopeful predictions. The primary drivers of green OA are policies at universities and funding agencies. Remember, all university policies allow publishers to protect themselves at will. (See section 4.1 on policies.) For example, universities with loophole or deposit mandates will not provide green OA when publishers do not allow it. Universities with Harvard-style rights-retention mandates will not provide OA when authors obtain waivers or when publishers require authors to obtain waivers as a condition of publication. Hence, publishers who worry about the effect of university OA policies on subscriptions have the remedy in their own hands. Faculty needn’t paternalize publishers by voting down OA policies when publishers can protect themselves whenever they see the need to do so. The experience at Harvard since February 2008 is that very few publishers see the need to do so. Fewer than a handful systematically require waivers from Harvard authors. This chapter, then, focuses on the strongest green OA mandates at funding agencies, like the Wellcome Trust and NIH, which allow no opt-outs for publishers or grantees. Will strong green OA policies of that kind trigger cancellations of toll-access journals? Here are 10 parts of any complete answer. 1. Nobody knows yet how green OA policies will affect journal subscriptions. Rising levels of green OA may trigger toll-access journal cancellations, or they may not. So far they haven’t. 2. The evidence from physics is the most relevant. Physics has the highest levels and longest history of green OA. The evidence from physics to date is that high levels of green OA don’t cause journal cancellations. On the contrary, the relationship between arXiv (the OA repository for physics) and toll-access physics journals is more symbiotic than antagonistic. Physicists have been self-archiving since 1991, far longer than in any other field. In some subfields, such as particle physics, the rate of OA archiving approaches 100 percent, far higher than in any other field. If high-volume green OA caused journal cancellations, we’d see the effect first in physics. But it hasn’t happened. Two leading publishers of physics journals, the American Physical Society (APS) and Institute of Physics (IOP), have publicly acknowledged that they’ve seen no cancellations attributable to OA archiving. In fact, the APS and IOP have not only made peace with arXiv but now accept submissions from it and even host their own mirrors of it. 3. Other fields may not behave like physics. We won’t know more until the levels of green OA in other fields approach those in physics. It would definitely help to understand why the experience in physics has gone as it has and how far it might predict the experience in other fields. But so far it’s fair to say that we don’t know all the variables and that publishers who oppose green OA mandates are not among those showing a serious interest in them. When publisher lobbyists argue that high-volume green OA will undermine toll-access journal subscriptions, they don’t offer evidence, don’t acknowledge the countervailing evidence from physics, don’t rebut the evidence from physics, and don’t qualify their own conclusions in light of it. They would act more like scientific publishers if they acknowledged the evidence from physics and then argued, as well as they could, either that the experience in physics will change or that fields other than physics will have a different experience. she merely asserts the threat. This style of rebuttal will not do. . . .” For more than eight years, green OA mandates have applied to research in many fields outside physics. These mandates are natural experiments and we’re still monitoring their effects. At Congressional hearings in 2008 and 2010, legislators asked publishers directly whether green OA was triggering cancellations. In both cases, publishers pointed to decreased downloads but not to increased cancellations. 4. There is evidence that green OA decreases downloads from publishers’ web sites. When users know about OA and toll-access editions of the same article, many will prefer to click through to the OA edition, either because they aren’t affiliated with a subscribing institution or because authentication is a hassle. Moreover, when users find an OA edition, most stop looking. But decreased downloads are not the same thing as decreased or canceled subscriptions. Moreover, decreased downloads of toll-access editions from publisher web sites are not the same thing as decreased downloads overall. No one suggests that green OA leads to decreased overall downloads, that is, fewer readers and less reading. On the contrary, the same evidence suggesting that OA increases citation impact also suggests that it increases readers and reading. 5. Most publishers voluntarily permit green OA. Supplementing the natural experiments of green OA mandates are the natural experiments of publishers who voluntarily permit green OA. The Nature Publishing Group is more conservative than most toll-access publishers by requiring a six-month embargo on green OA, but more progressive than most by positively encouraging green OA. NPG reported the latest results of its multidisciplinary natural experiment in January 2011: “We have, to date, found author self-archiving compatible with subscription business models, and so we have been actively encouraging self-archiving since 2005.” 6. Green OA mandates leave standing at least four library incentives to maintain their subscriptions to toll-access journals. Even the strongest no-loophole, no-waiver policies preserve incentives to maintain toll-access journal subscriptions. Medknow saw its submissions and subscriptions increase when it began offering unembargoed full-text editions of its journals alongside its toll-access print journals. Hindawi Publishing saw its submissions rise steadily after it converted all its peer-reviewed journals to OA in 2007. Looking back on several years of rapidly growing submissions, company founder and CEO Ahmed Hindawi said in January 2010, “It is clear now more than ever that our open access conversion . . . was the best management decision we have taken. . . .” 9. Some publishers fear that green OA will increase pressure to convert to gold OA. Some publishers fear that rising levels of green OA will not only trigger toll-access journal cancellations but also increase pressure to convert to gold OA. (Likewise, some OA activists hope for this outcome.) 10. Green OA policies are justified even if they do create risks for toll-access journals. If we’re only interested in the effect of rising levels of green OA on toll-access publishers, then we can stop at points 1–9. But if we’re interested in good policy, then we must add one more factor: Even if green OA does eventually threaten toll-access journal subscriptions, green OA policies are still justified. I won’t elaborate this point here, since it takes us beyond the topic of casualties to the full case for OA, which is spread throughout the rest of the book. But here’s one way to put the debate in perspective: There are good reasons to want to know whether rising levels of green OA will trigger cancellations of toll-access journals, and perhaps even to modify our policies in light of what we learn. But there are no good reasons to put the thriving of incumbent toll-access journals and publishers ahead of the thriving of research itself.

<question>:
What is most likely the author's purpose for writing this?

<options>:
A To inform us of the differences between gold OA, green OA, and TA
B To explain how green OA is improving publishing
C To persuade the reader that green OA is useful
D To explain how universities are handling green OA

<answer>:

C