Also called 2-3-4 tree. A node has at-least 2 children. Can have 2, 3 or 4 child.
Can be easily converted to Red-Black Tree.
a-b Tree aka Multi-way Search Tree
Minimum number of nodes a, maximum. Thus, minimum number of keys is a-1 and maximum b-1.
What is the relationship between a & d?
a-1<=(d-1)/2
The height of the B-Tree would vary from logbn to logan