Consider the following $2-3-4$ tree (i.e., B-tree with a minimum degree of two) in which each data item is a letter. The usual alphabetical ordering of letters is used in constructing the tree.
What is the result of inserting $G$ in the above tree?
D. None of the above
(B) is the correct answer.
Once we add $G$, the leaf node becomes $B \ G \ H \ I$, since we can have only $3$ keys. the node has to split at $G$ or $H$, and $G$ or $H$ will be added to parent node.
Since $P$ is the parent node in options $1$ and $2$, its evident the $3$rd element i.e. $H$ should be selected for splitting (because after adding any key from the leftmost child node, $P$ becomes the $3$rd element in the node)
Now parent node becomes $H \ L \ P \ U$, select $P$ as for splitting, and you get option B.
Hence, answer is B.
When we get BGHI, why can't H go up? How can we say G must go up- because both are median.