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.

When it interacts with ryanodine receptors, this element upregulates its own release, and this compound forms the cell plates of coccolithophores. Stimulation of Gq ("g-sub-q") opens a channel that allows for this ion's movement, and proteins that bind this ion have an EF hand motif. Cellular concentrations of this ion are regulated by IP3. Parafollicular cells of the (*) thyroid produce a compound that reduces the concentration of this ion in blood, and its intestinal absorption requires vitamin D. This ion interacts with Troponin to stimulate muscle contraction, and the lumens of sarcoplasmic reticula have high concentrations of this ion. For 10 points, name this divalent cation that is stored in bones.
Science

Norman and Jensen created triangles in which they plot chemical species according to this quantity. In one model of this quantity, electrons distribute to minimize it. Besides the Allred-Rochow definition, Mulliken's original definition of this quantity involved taking the mean of the(*) electron affinity and the first ionization energy. Dissociation energies between two elements are used to calculate the Pauling scale of this quantity, on which fluorine has the highest value. For 10 points, name this property that refers to an atom's ability to attract electrons.
Science

This economist posited an early form of the Quantity Theory of Money in Tract on Monetary Reform. He proposed that recessions can get worse in the presence of near-zero nominal interest due to liquidity traps, and that an increase in GDP can result from initial investment through the multiplier effect. He argued against reparations in a work critical of the Treaty of Versailles, The Economic Consequences of the Peace, and in another work for increased government spending to combat recessions. For 10 points, name this writer of The General Theory of Employment, Interest and Money.

Social Science