Which license should be chosen in arXiv for a paper to be published in Elsevier? I would like to know what license needs to be chosen in arXiv for a paper that is to be sent to an Elsevier journal. I have read the terms of both arXiv and Elsevier attentively, but I'm still in doubt.

arXiv has the following choices for licenses (from their website):


  
  grant arXiv.org a non-exclusive and irrevocable license to distribute the article, and certify that he/she has the right to grant
  this license;
  certify that the work is available under one of the following Creative Commons licenses and that he/she has the right to assign this
  license:
  
  
  Creative Commons Attribution license (CC BY 4.0)
  Creative Commons Attribution-ShareAlike license (CC BY-SA 4.0)
  Creative Commons Attribution-Noncommercial-ShareAlike license (CC BY-NC-SA 4.0);
  
  or dedicate the work to the public domain by associating the Creative Commons Public Domain Dedication (CC0 1.0) with the
  submission.
  


On the other hand, Elsevier explicitly allows to publish accepted manuscripts in arXiv, provided it's "updating a preprint", not creating a new one (a really strange requirement in my view, whose motivation I've never understood, but that is the subject of a different question) and provided that this is done with a CC-BY-NC-ND license, which is none of the above. From their website:


  Authors can share their accepted manuscript:
  
  Immediately (...) by updating a preprint in arXiv or RePEc with the
  accepted manuscript (...) In all cases accepted manuscripts should
  (...) bear a CC-BY-NC-ND license.


How are those two things reconciled, as arXiv doesn't have the option of using a CC-BY-NC-ND license? There should be a way, as otherwise the mentions of arXiv in the Elsevier policy would be totally pointless - allowing you explicitly to publish on a site with a license that that site won't allow! Is it legal to choose "grant arXiv.org a non-exclusive and irrevocable license" and upload the manuscript with a CC-BY-NC-ND license? Would this mean that the first license is for arXiv and the second license is for the rest of the world? This is the only solution to the puzzle I can think of, but I don't know if it stands (it seems that one needs a degree in law to understand these kind of copyright conditions...)
How to add another Creative Commons license to an arXiv paper:


  We currently support three of the Creative Commons licenses. If you wish to use a different CC license, then select arXiv's non-exclusive license to distribute in the arXiv submission process and indicate the desired Creative Commons license in the actual article.


From the arXiv webpage about licenses.

How to indicate the desired Creative Commons license according to Elsevier:


  Elsevier requires authors posting their accepted manuscript to attach a non-commercial Creative Commons user license (CC-BY-NC-ND).  This is easy to do. On your accepted manuscript add the following to the title page, copyright information page, or header /footer: © YEAR. Licensed under the Creative Commons [insert license details and URL].


From Elsevier's sharing webpage.