The efficinecy for solving the towers of hanoi problem recursively
a. o(n2)
b. o(2n)
c. o(logn)
d. o(n)

B.O(2n)

Explanation:

The time complexity of solving towers of hanoi problem recursively is O(2n) because there are two recursion calls in the solution of tower of hanoi.First recursive call to move n-1 disks to from source to helper then the user moves nth disk from source to destination after that recursion moves n-1 disks from helper to destination using source as helper rod.So each recursive call make two more recursive call this makes the time complexity be O(2n).