If we consider this just as B tree, order of tree is 4.
Because minimum degree is 2.
Then m/2 = 4, m =4. (As it is upper bound, m can not be 5, m = Order of tree.)
If we insert G leaf node B H I becomes B G H I. As we can have maximum 3 keys in any node, we split it. G Goes up !
Then root becomes G,L,P,U.
Then We need to split root. L becomes root.
Answer -> D