In this task you will be given a text passage from a trivia quiz. You should choose the category this question belongs to from these categories: History, Science, Social Science, Fine Arts, Literature. You can only choose one category, so if in doubt, please choose the closest match.

The dancing variety, employed in the Reiser4 file system, delays optimization until a flush-to-disk command is issued. One variety of them, invented by Sleator and Tarjan, rearranges the entire structure without storing any bookkeeping work, and is known as the splay type, but it lacks the worst-case guarantee of O(log n) [big O of log n] run-time present in the AVL type. The B variety may have a variable number of keys, and the one named after Arne and Andersson is a specific case of the red-black variety, which employs a balancing algorithm that checks the color of each of its nodes. All children to the left of a root are less than those at the root in the binary-search type of, FTP, which type of data structure whose nodes at the bottommost level are called leaves
Science