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

<passage>:
mandates These merely ask faculty to make their work OA, or recommend OA for their new work. Sometimes they’re called resolutions or pledges rather than policies. all OA mandates are green. Unfortunately, however, many people mistakenly believe that all OA is gold OA and therefore mistake proposed green OA mandates for proposed gold OA mandates and raise objections that would only apply to gold OA mandates. But as more academics understand the green/gold distinction, and understand that well-written green OA mandates are compatible with academic freedom, more institutions are adopting green OA mandates, almost always at the initiative of faculty themselves. At universities, there are roughly three approaches to green OA mandates: Loophole mandates These require green OA except when the author’s publisher doesn’t allow it. Deposit mandates Deposit mandates generally depend on publisher permission for OA, just like loophole mandates. The difference is that they require deposit even when they can’t obtain permission for OA. Rights-retention mandates First note that none of the three “mandates” absolutely requires OA. Loophole mandates allow some work to escape through the loophole. Deposit mandates allow some deposited work to remain dark (non-OA), by following publisher preferences. Rights-retention mandates with waiver options allow some work to remain dark, by following author preferences. Loophole and deposit policies defer to publishers for permissions, while rights-retention policies obtain permission from authors before they transfer rights to publishers. For loophole and deposit policies, permission is contingent, because some publishers are willing and some are not. For rights-retention policies, permission is assured, at least initially or by default, although authors may opt out for any publication. When loophole policies can’t provide OA, covered works needn’t make it to the repository even as dark deposits. When deposit and rights-retention policies can’t provide OA, at least they require dark deposit for the texts, and OA for the metadata (information about author, title, date, and so on). Releasing the metadata makes even a dark deposit visible to readers and search engines. Moreover, many repositories support an email-request button for works on dark deposit. The button enables a reader to submit a one-click request for a full-text email copy and enables the author to grant or deny the request with a one-click response. Many institutions adopt loophole policies because they believe a blanket exemption for dissenting publishers is the only way to avoid copyright problems. But that is not true. Deposit policies don’t make works OA until publishers allow OA, and rights-retention policies close the loophole and obtain permission directly from authors at a time when authors are the copyright holders. OA policies from funding agencies are very much like OA policies from universities. They can encourage green and gold OA, or they can require green OA. If they require green OA, they can do so in one of the three ways above. If there’s a difference, it’s that when funders adopt a rights-retention mandate, they typically don’t offer waiver options. On the contrary, the Wellcome Trust and NIH require their grantees to make their work OA through a certain OA repository on a certain timetable and to retain the right to authorize that OA. If a given publisher will not allow grantees to comply with their prior funding agreement, then grantees must look for another publisher. There are two reasons why these strong funder policies don’t infringe faculty freedom to submit work to their journals of their choice. First, researchers needn’t seek funds from these funders. When they choose to do so, then they agree to the OA provisions, just as they agree to the other terms and conditions of the grant. The OA “mandate” is a condition on a voluntary contract, not an unconditional requirement. It’s a reasonable condition as well, since public funders, like the NIH, disburse public money in the public interest, and private funders, like the Wellcome Trust, disburse charitable money for charitable purposes. To my knowledge, no researchers have refused to apply for Wellcome or NIH funds because of the OA condition, even when they plan to publish in OA-averse journals. The OA condition benefits authors and has not been a deal-breaker. 4.3 Digression on the Historical Timing of OA Policies Some kinds of strong OA policy that are politically unattainable or unwise today may become attainable and wise in the future. Here are three examples. Today, a libre green mandate (say, one giving users the right to copy and redistribute, not just access for reading) would face serious publisher resistance. Even if the policy included rights retention and didn’t depend on publishers for permissions, publisher resistance would still matter because publishers possess—and ought to possess—the right to refuse to publish any work for any reason. They could refuse to publish authors bound by a libre green policy, or they could insist on a waiver from the policy as a condition of publication. Policies triggering rejections hurt authors, and policies driving up waiver rates don’t do much to help OA. However, publisher resistance might diminish as the ratio of OA publishers to toll-access publishers tilts toward OA, as spontaneous author submissions shift toward OA journals, or as the number of institutions with libre green mandates makes resistance more costly than accommodation for publishers. When OA policies are toothless, few in number, or concentrated in small institutions, then they must accommodate publishers in order to avoid triggering rejections and hurting authors. But as policies grow in number, scope, and strength, the situation could flip over, and publishers will have to accommodate OA policies in order to avoid hurting themselves by rejecting too many good authors for reasons unrelated to the quality of their work. Today, a gold OA mandate would limit faculty freedom to submit work to the journals of their choice. But that’s because today only about 25 percent of peer-reviewed journals are OA. As this percentage grows, then a gold OA mandate’s encroachment on academic freedom shrinks. At some point even the most zealous defenders of faculty freedom may decide that the encroachment is negligible. In principle the encroachment could be zero, though of course when the encroachment is zero, and gold OA mandates are harmless, then gold OA mandates would also be unnecessary. Today, faculty voting for a rights-retention OA mandate want a waiver option, and when the option is available their votes tend to be overwhelming or unanimous. But there are several circumstances that might make it attractive for faculty to abolish waiver options or make waivers harder to obtain. One is a shift in faculty perspective that makes access to research more urgent than indulging publishers who erect access barriers. Another is a significant rise in publisher acceptance of green OA, which gives virtually all authors—rather than just most—blanket permission for green OA. In the first case, faculty might “vote with their submissions” and steer clear of publishers who don’t allow author-initiated green OA. In the second case, faculty would virtually never encounter such publishers. In the first case, they’d seldom want waivers, and the second they’d seldom need waivers. It’s understandable that green gratis mandates are spreading faster than green libre mandates, that green mandates in general are spreading faster than gold mandates, and that rights-retention policies with waiver options are spreading faster than rights-retention policies without waivers. However, there is modest growth on one of these fronts: green libre mandates.

<question>:
Why are green gratis mandates spreading faster than green libre mandates

<options>:
A Gold mandates are more popular than libre green mandates
B University resistance to libre green mandates
C Author resistance to libre green mandates
D Publisher resistance to libre green mandates

<answer>:

D