In which tree, for every node the height of its left subtree and right subtree differ almost by 1?
AVL tree is a self-balancing Binary Search Tree (BST) where the difference between heights of left and right sub-trees cannot be more than one for all nodes.
Hence,Option(B) AVL Tree is the correct choice.
Although the fact you given here for complete binary tree is likely to AVL tree, but the purpose of self balancing binary search tree is different than complete binary tree.
In complete binary no such properties(i.e. every node the height of its left subtree and right subtree differ almost by 1) holds.
Also self balancing binary search tree is used for other data structure such as priority queue.Self-balancing binary search trees can be used to construct and maintain ordered lists
These are available Self balancing binary search tree..
Arjun sir can give more clarity here.