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]: This man achieved full power within his party at the Zunyi Conference. That conference occurred while this man and other members of his party were traveling from Jiangxi (jee-AHNG-shee) to Yanan as part of the Long March. This leader's third wife was part of an influential group that was named the Gang of Four. This ruler was responsible for his country taking part in the (*) Great Leap Forward and the Cultural Revolution. For 10 points, name this political rival of Chiang Kai-shek who was the first leader of Communist China.
[EX A]: History

[EX Q]: An approximation of it named for Russell uses the TDS value to determine one of its parameters via the Langelier approximation, while one constant that appears in it has units of moles per kilogram to the one half power, according the Bates-Guggenheim convention. Along with Guggenheim, Scatchard and Bronsted improved upon this model by developing the SIT theory, and that model has a better fit than a modification of it named for Davies. This relationship assumes the existence of only long-range interactions, and it was extended to account for Brownian motion by Lars Onsager. It assumes that the solvent is structure-less and that the solution is dilute, and the theory behind it implies that the electrostatic potential falls off exponentially when r is greater than the atomic radius due to screening by counter ions. For 10 points, identify this equation which is used to calculate the activity coefficients, and is named for a German and a Dutch scientist. 
[EX A]: Science

[EX Q]: One modification of this reaction uses an active hydrogen compound with two strong electron-withdrawing groups in order to synthesize a conjugated enone and is named for Knoevanagel, and Evans used a chiral oxazolidinone auxiliary to make it stereoselective. Many of its derivatives follow the Zimmerman-Traxler mechanism, with the exception of the version using a silyl enol ether known as the Mukiyama variation. It also follows a Michael addition in the two-step Robinson annulation, and its base catalyzed variant creates an enolate nucleophile which then attacks a carbonyl. FTP, name this condensation reaction whose namesake product is a beta-hydroxy ketone.
[EX A]:
Science