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.

Input: Consider Input: 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.

Output: Science

Input: Consider Input: Slogans which became popular in this country included "we don't want to be slaves anymore" and "down with the government, down with the police." This country was home to the underground Christian organization Young Congregation, which helped instigate an event whose nine demands were issued by the Bitterfeld committee, the most influential of the workers' councils which emerged here. People in this country received boxes containing peas, flour, milk, and lard that were known as (*) Eisenhower Packages. After this country announced the New Course program, replacing Constructing Socialism, and including a ten percent increase in production quotas, workers walked out onto Stalin Alley. In this country, where the play The Plebeians Rehearse the Uprising takes place, Soviet tanks were deployed to end a 1953 popular uprising. For 10 points, identify this country which erupted into mass demonstrations against Walter Ulbricht's regime.

Output: History

Input: Consider Input: The normal mechanism of the formation of these is altered in Chevrel and A15 phases. Generally, their constituents are not physically near each other, but are closely related in momentum space. A proposed method of splitting them is to send them through a carbon nanotube to form a Luttinger liquid. Evidence of their existence was supplied by the isotope effect, and the exchange of phonons results from their coupling. For 10 points -- name these groups that explain charge-carrier tunneling effects, paired electrons that form the basis of the BCS theory.
Output: Science