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

The second part of this poem describes a figure "whose love is endless oil and stone" and "whose   name is the Mind!". The third section of this poem tells of a place "where the faculties of the skull no  longer admit the worms of the senses". This poem was judged to be not obscene when its publisher,   Lawrence Ferlinghetti, was put on trial. "Mohammedan angels staggering on tenement roofs" appear  in this poem dedicated to Columbia Psychiatric Institute patient Carl Solomon, whom the poet  repeatedly tells "I'm with you in Rockland." Name this poem that describes Moloch, and opens "I  saw the best minds of my generation destroyed by madness", written by Allen Ginsberg.
Literature

One section of these materials is known as the depletion zone. These materials are characterized by a small gap between the Fermi level and the valence band. Impurities are added to these materials in order to create either extra electrons or electron holes in the N- and P-types of these materials, respectively. That process is called (*) doping. These materials, such as germanium and gallium arsenide, are used in electronic devices such as diodes and transistors. For 10 points, name these materials, such as silicon, that have electrical conductivity in between that of a conductor and an insulator.

Science

