Answer is d
All the statement are correct
Option a :
The height of an AVL is bound by 1.44log n
option b )
If it is LL and RR then it would have 1 rotation only
But if LR and RL then it would have 2 rotation .
So atmost 2 rotation would required if AVL tree are not balanced .
Option c
AVL is favourable over skewed tress have complexity of O(N) for deletion
But AVL are balanced tree so it would require logn for deletion
:) You can see this also
http://www.geeksforgeeks.org/avl-tree-set-1-insertion/