In a B+ tree, the requirement of at least half-full (50%) node occupancy is relaxed for which one of the following cases?
Answer
(A)
Explanation
Every node of a B+ tree except the root must be at least half full: an internal node of order \(p\) needs at least \(\lceil p/2 \rceil\) children, and a leaf must fill about half of its key slots. This keeps the tree shallow and its space use predictable.
The root cannot always meet the rule. When the root splits, the new root starts with a single key and two children, and a small tree may hold fewer keys than half a node. So the root alone is exempt: it needs only two children, or a single key when it is also a leaf.
Leaves, internal nodes and the leftmost leaf get no such exception, so B, C and D are wrong.
Answer: A