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]: 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.
[EX A]: Science

[EX Q]: This element's only oxidation state is -1, and it is impossible to free from its compounds by chemical means. It is prepared commercially be the same method which Henri Moisson used to isolate it in 1886, and is also found in the mineral cryolite. Its only isotope is the stabe 19 version, and in its gaseous form takes on a pale yellow color. The most electronegative and reactive of the elements, FTP, what is this lightest of the halogens with atomic number 9 and symbol F
[EX A]: Science

[EX Q]: This work approvingly quotes Schopenhauer's advice to a dishonest guardian on how to keep a ward from growing too intelligent. This work satirizes one concept as resembling the story of "Tono, the Great Dane" who forms his idea of the "Great Dog" after his own attributes, leading to the happy conclusion he is the Great Dog. It praises piecemeal engineering over utopian engineering because of the latter's want of large scale social experimentation. Besides "Nature and Convention", and "Aestheticism, Perfectionism, and Utopianism", this work's second volume dicsusses "The Rise of Oracular Philosophy" and "Hegel and the New Tribalism. " The first volume classifies one man as a great sociologist but decries him for a vision of fascism and totalitarianism. Opening with a chapter on "The Spell of Plato", for 10 points name this defense of liberal democracy by Karl Popper.
[EX A]:
Social Science