Option B is the answer.
1. T(n) = T(n-1) + 1/n
Apply substitution ,
T(n) = 1+1/2 + 1/3 + 1/4 +1/5 +... +1/n
T(n) = O(logn)
2. T(n) = 2T(n/2) + n/logn
Apply master theorem
T(n)= O(nloglogn)
3.T(n) = sqr root (n).T(sqr root (n)) + n
T(n)= O(nloglogn)
4.T(n) = 4T(n/2) + n^2(sqr root(2))
Apply master theorem
T(n)= O(n^2.5)