A max-heap is a heap where the value of each parent is greater than or equal to the value of its children. Which of the following is a max-heap?
in option (A) - it is not a max heap because it is not Almost Complete Binary Tree .
in option (C) - it is complete binary tree but not follow the max heap property i.e. the values of parent nodes always greater then child nodes
and there node of value $5$ is less then on e of its children.
in option (D) - similar to above (C) option explanation here node of value $2$ is less then to the value $4$ .
correct option is (B) that is satisfy both properties and all of the max heap .
in option (A) - it is not a max heap because it is not complete binary tree
@ASHU2015 correct this line
it is not a max heap because it is not Almost Complete Binary tree. Because Heap Must Be Complete binary tree or almost complete binary tree.