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.

[EX Q]: A maximum independent set for this data structure can be found in linear time by adding alternating levels. In this structure, any two vertices or nodes must be connected by a single simple path, and thus it is connected and acyclic. By using (*) union-find with disjoint sets, one type of this structure containing all the vertices of a connected graph can be constructed. One variety of this data structure can be used to easily implement a binary search. This structure also comes in red-black and self-balancing-binary varieties. For 10 points, identify this data structure from computer science, a hierarchical graph in which "leaf" nodes ultimately flow from a "root" node.
[EX A]: Science

[EX Q]: A territory invaded during this war asked to borrow gunpowder to salute a ship that had come to conquer it. One island invaded in this war had been overseen by the "Butcher" Weyler. An admiral in this war stated "You may (*) fire when you are ready," prior to beginning the Battle of Manila Bay. One battle in this "splendid little war" saw San Juan Hill charged upon by the Rough Riders and Teddy Roosevelt. Hearst's and Pulitzer's yellow journalism as well as the explosion of the USS Maine helped instigate this war. For 10 points, name this war which led to the capture of the Philippines, Puerto Rico, and Cuba by the United States.
[EX A]: History

[EX Q]: Members of the genus aeromonas have polar and lateral types of these, and it has a paracrystalline filament running along its length in T. brucei. In some organisms, a MS ring and a periplasmic P ring are found at its base, and a June 2008 study in Science discusses a protein that acts a clutch to halt the rotation of these. Their components are connected by nexin linkages, and dyneins generate the force which causes a bending motion in eukaryotes, wherein they have a 9+2 arrangement of microtubules that form an axoneme. For 10 points, identify these structures consisting of hooks and filaments in basal bodies, present in euglena and sperm cells, which allow for motility of the cells.
[EX A]:
Science