Given that n arithmetic means are inserted between two sets of numbers a,2b, and 2a,b where a,b, `inR`. Suppose further that `m^(th)` mean between these two sets of numbers are same, then the ratio a:b equals
A. `n-m+1:m`
B. `n-m+1:n`
C. `m:n-m+1`
D. `n:n-m+1`
