Which ones of this are an oxidation-reduction reaction? and why?
(A) Hcl (aq) → H+(aq) + cl-(aq) (B) CH4 + cl2 → CH3cl + Hcl
(C) 2 CrO4 2-+ 2H+ → Cr2O72-+ H2O (D) Zn + Hcl → Zncl 2 + H2

I'm learning about the periodic tables and what each subject's configuration is. for example, hydrogen is 1s^1, but i don't understand how you get that. can someone me understand how to figure out how to figure this out? sorry if the question makes no sense, but it would really a lot if you could me understand! you so much if you can!