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.

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.
Science

In one story, this man saved the town of Gubbio by making a pact with an attacking wolf. After spending time as a Perugian captive, he saw a vision of a hall full of cross-marked armor, which encouraged him to travel to Apulia. After 40 days' fasting on the mountain La Verna, he saw a six-winged seraph, after which he received the stigmata, according to his namesake Fioretti. He praised Sister Death, Brother Fire, and Brother Moon in his Canticle of the Sun, and was credited with inventing the Nativity creche scene. For 10 points, identify this Catholic patron saint of animals, the founder of a namesake group whose first two orders are the Poor Clares and the Friars Minor.
History

After defeating an invading force from Mesopotamia that kidnapped his nephew, this man was blessed by the king of Salem, named Melchizedek. Because of his wife's beauty, he lied that they were siblings, which caused both Pharoah and Abilimech to try to marry her. This man died five years early to be spared of the pain of seeing the sale of his grandson Esau's birthright. This man's wife was infertile so he laid with his handmaiden Hagar. For 10 points, name this Biblical figure who almost sacrificed his son Isaac to God on Mount Horeb and whose name means "father of many nations," the patriarch of Islam, Christianity, and Judaism.

Social Science