If `S_1` is the sum of an AP of `n` odd number of terms and `S_2` be the sum of terms of series in odd places of the same AP, then `(S_1)/(S_2)=`
a.     `(2n)/(n+1)`
b.     `n/(n+1)`
c.     `(n+1)/(2n)`
d.     `(n+1)/n`