TASK DEFINITION: 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.
PROBLEM: 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.

SOLUTION: Science

PROBLEM: This man reformed the fyrd militia system so that it fought in shifts, allowing for the creation of a standing army without disrupting agriculture. In addition to establishing the burhs system of forts, this man built a secret military base on the swamp island of Athelney. This mans advisors included Bishop Asser, who wrote an early biography of him. This author of the so-called doom book won control of all territory west of Watling Street when he won the Battle of Edington against Guthrum the Old. Apart from translating many religious works into English, he is best known for ending the Danegeld. For ten points, name this King of Wessex, the only English monarch with the epithet the Great.

SOLUTION: History

PROBLEM: sum of the squares of the reciprocals of this function evaluated at the nonnegative integers is equal to the modified Bessel function of the first kind at x=2. The Leviathan Number is found by evaluating this function at 10 to the 666th power. The rising type can be represented with the Pochhammer Symbol. Wilson's Theorem states that this function of any prime minus 1 is also congruent to -1 modulo that prime. Legendre's theorem provides a corollary to determine the number of (*) trailing zeroes of this function evaluated at nonnegative integers. When this function is evaluated at large numbers, Stirling's approximation is used. The gamma function extends this function to all complex numbers other than negative integers. For 10 points, name this function that, for positive integers n, is the product from 1 to n, and which is represented by an exclamation point.

SOLUTION:
Science