我的文章已经被录用了，版权协议也已经发过去了，可出版社突然给我发了如下这样一个邮件：
>Articles in Remote Sensing - Theory and Methods are eligible for iOpenAccess. Electing this option allows the article to be made freely available online under a Creative Commons License. The iOpenAccess service requires registration with Rightslink, and payment of a fee. Selection of iOpenAccess is strictly at the author's discretion, and is not required for publication.
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不知道是什么意思，请大家给为帮帮忙，说明一下我该怎么操作？谢谢