Problem: H2 is a product of some types of anaerobic metabolism and is produced by several microorganisms, usually via reactions catalyzed by iron- or nickel-containing enzymes called hydrogenases. These enzymes catalyze the reversible redox reaction between H2 and its component two protons and two electrons. Creation of hydrogen gas occurs in the transfer of reducing equivalents produced during pyruvate fermentation to water. The natural cycle of hydrogen production and consumption by organisms is called the hydrogen cycle.
What is the natural cycle of hydrogen production and consumption by organisms called?
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Answer: hydrogen cycle

Problem: Under Article IV, Section Three of the United States Constitution, which outlines the relationship among the states, Congress has the power to admit new states to the union. The states are required to give "full faith and credit" to the acts of each other's legislatures and courts, which is generally held to include the recognition of legal contracts, marriages, and criminal judgments. The states are guaranteed military and civil defense by the federal government, which is also obliged by Article IV, Section Four, to "guarantee to every state in this union a republican form of government".
What are all states guaranteed by the republican form?
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Answer: unanswerable

Problem: The original Latin word "universitas" refers in general to "a number of persons associated into one body, a society, company, community, guild, corporation, etc." At the time of the emergence of urban town life and medieval guilds, specialised "associations of students and teachers with collective legal rights usually guaranteed by charters issued by princes, prelates, or the towns in which they were located" came to be denominated by this general term. Like other guilds, they were self-regulating and determined the qualifications of their members.
What did a universitas have in common with similar guilds?
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Answer:
they were self-regulating