Submit to arxiv prior to a conference or journal I'm about to apply for phd soon. I have several papers that I'm currently working on that are almost finished. That said, there is probably not enough to publish them on time. I think it might be a good idea to post them to arxiv so that I can point admission committee to my work as "preprints" in my application. But since I hope to eventually submit them to a journal or conference, what would be appropriate way to do it? for example, which license of the following should I choose? What are the difference? Would that affect my later publication?

arXiv.org perpetual, non-exclusive license to distribute this article (Minimal rights required by arXiv.org)

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)

Creative Commons Public Domain Declaration (CC0 1.0)
 None of the above licenses apply
This differs by field. Your profile suggests you are a mathematician and in math, almost all journals will publish papers previously available at arXiv. 

The life sciences seem to be an exception with many journals refusing to publish anything previously published, even if informally. Wikipedia gives some guidance. 

I'll leave the issue of license to the other questions linked in comments.