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]: composer of this opera was convinced to pursue it by his friend Sybil Seligman, who commissioned a translation of its text. At one point, a character reads the Fifty-first Psalm of David, though the original text had a book entitled "Old Joe Miller's Jokes. " Another character expresses frustration in the first act by declaring "Che terra maledetta," after which the romantic conflict is established by the aria "Chi c'e per farmi I ricci" In the second act, another character's knowledge of Nina Micheltorena is asked into by Ashby, and later that character sings the aria "Ch'ella mi creda libero. " Based on a play by David Belasco, it also features Wowkle and Billy, who are urged to marry in a church, and Jim Larkens who simply longs to go home. Ramirez is the secret identity of Dick Johnson, who is saved by his beloved Minnie. FTP, name this opera set in the American west, by Puccini.
[EX A]: Fine Arts

[EX Q]: In 2007, this city began a controversial underground rail project called the Crossrail. In 2009, its mayor, Boris Johnson, saved a woman from a mugging while biking to work. In 2005, this city was rocked by a series of coordinated terrorist attacks on July 7. This city is in the process of constructing an Aquatics Centre, a Velopark (VELL-oh-park), and a Handball Arena as it is hosting the 2012 Summer Olympics. For 10 points, name this capital of the United Kingdom.
[EX A]: Fine Arts

[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