a B-tree of order m is a tree which satisfies the following properties:
Every node has at most m children.
Every non-leaf node (except root) has at least ⌈m/2⌉ children. The root has at least two children if it is not a leaf node.
so it has a minimum of m/2 children .. that means in between ⌈m/2⌉ and m
seems to be some printing mistake between A and D. answer will be ⌈m/2⌉ and m