The $2-3-4$ tree is a self-balancing data structure, which is also called :
Option A
a 2–3–4 tree (also called a 2–4 tree) is a self-balancing data structure that is commonly used to implement dictionaries. The numbers mean a tree where every node with children (internal node) has either two, three, or four child nodes:
2-node
3-node
4-node
for more details https://en.wikipedia.org/wiki/2%E2%80%933%E2%80%934_tree