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.

[Q]: One king of this name and number married Joan of Navarre and fended off the "Epiphany Uprising. " Another king by this name and number had Maximilian de Bethune, Duke de Sully negotiate the Peace of Savoy, but was assassinated by Francois Ravalliac. Yet another ruler of this name and number dealt with the rise of anti-king Rudolf of Swabia, and had installed Clement III as pope, though he had earlier traveled to Canossa to reconcile with Pope Gregory VII. For 10 points, identify this name and number shared by the Holy Roman Emperor involved in the Investiture controversy as well as the Bourbon king of Navarre who declared that "Paris is worth a Mass. "
[A]: History

[Q]: When these devices exploit their voltage-dependent variable capacitance they are known as varactors. Barring the creation of local hot spots, a non-destructive avalanche current is produced by electron-hole pair propagation when the electric field within the (*) depletion region of these devices reaches a critical value. Majority carriers exist in an energy state greater than the Fermi energy in the Schottky barrier variety and those that operate in reverse breakdown are named after Zener. For 10 pointsname these devices that allow current to pass in only one direction.
[A]: Science

[Q]: Otto Stern proposed a slipping plane in these systems, at which ions with non-negligible volume adsorb to a surface, modifying the Helmholtz and Gouy-Chapman models. These systems are stabilized through the addition of a salt, called peptization. Because these materials effectively scatter light with low wavelengths, they often appear blue when light is shined through them in the Tyndall effect. Flocculation disrupts these systems, which are defined to be dispersions with particle diameter between a nanometer and a micrometer. For 10 points, name these systems of in which one substance is dispersed throughout another, exemplified by foams, emulsions, and aerosols.
[A]:
Science