In a B+ tree, the root node serves as the entry point for accessing data in the tree. Unlike internal and leaf nodes, the root node may not have strict occupancy requirements due to its unique position and role within the tree structure. Allowing the root node to have less than half-full occupancy helps in accommodating changes in the tree's structure efficiently, especially during insertion and deletion operations. This relaxation ensures that the root node can adapt to varying data volumes and maintain a balanced tree structure. Therefore, option A, where only the root node has relaxed occupancy requirements, is the correct choice.
Correct Answer: A
