A. R = [m]\lim_{{n \to \infty}} \left| \frac{{a_{n+1}}}{{a_n}} \right|[/m]
B. R = [m]\lim_{{n \to \infty}} \left| \frac{{a_n}}{{a_{n+1}}} \right|[/m]
C. R = [m]\lim_{{n \to \infty}} \left| \frac{{a_{n-1}}}{{a_n}} \right|[/m]
D. R = [m]\lim_{{n \to \infty}} \left| \frac{{a_n}}{{a_{n-1}}} \right|[/m]