Problem: Uranium:

Salts of many oxidation states of uranium are water-soluble and may be studied in aqueous solutions. The most common ionic forms are U3+ (brown-red), U4+ (green), UO+
2 (unstable), and UO2+
2 (yellow), for U(III), U(IV), U(V), and U(VI), respectively. A few solid and semi-metallic compounds such as UO and US exist for the formal oxidation state uranium(II), but no simple ions are known to exist in solution for that state. Ions of U3+ liberate hydrogen from water and are therefore considered to be highly unstable. The UO2+
2 ion represents the uranium(VI) state and is known to form compounds such as uranyl carbonate, uranyl chloride and uranyl sulfate. UO2+
2 also forms complexes with various organic chelating agents, the most commonly encountered of which is uranyl acetate.

Along with uranyl sulfate and uranyl chloride, what compound is formed by the UO2+ 2 ion?
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A: uranyl carbonate

Problem: Napoleon:

Historians agree that Napoleon's remarkable personality was one key to his influence. They emphasize the strength of his ambition that took him from an obscure village to command of most of Europe. George F. E. Rude stresses his "rare combination of will, intellect and physical vigour." At 5 ft 6 in (168 cm), he was not physically imposing but in one-on-one situations he typically had a hypnotic impact on people and seemingly bent the strongest leaders to his will. He understood military technology, but was not an innovator in that regard. He was an innovator in using the financial, bureaucratic, and diplomatic resources of France. He could rapidly dictate a series of complex commands to his subordinates, keeping in mind where major units were expected to be at each future point, and like a chess master, "seeing" the best plays moves ahead.

How do historians describe Napoleon in his use of France's financial, bureaucratic, and diplomatic systems?
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A: an innovator

Problem: Southeast Asia:

The Jawa Dwipa Hindu kingdom in Java and Sumatra existed around 200 BCE. The history of the Malay-speaking world began with the advent of Indian influence, which dates back to at least the 3rd century BCE. Indian traders came to the archipelago both for its abundant forest and maritime products and to trade with merchants from China, who also discovered the Malay world at an early date. Both Hinduism and Buddhism were well established in the Malay Peninsula by the beginning of the 1st century CE, and from there spread across the archipelago.

Which Hindu kingdom existed around 200 BCE?
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A: Jawa Dwipa

Problem: Gregorian calendar:

The Gregorian calendar improves the approximation made by the Julian calendar by skipping three Julian leap days in every 400 years, giving an average year of 365.2425 mean solar days long. This approximation has an error of about one day per 3,300 years with respect to the mean tropical year. However, because of the precession of the equinoxes, the error with respect to the vernal equinox (which occurs, on average, 365.24237 days apart near 2000) is 1 day every 7,700 years, assuming a constant time interval between vernal equinoxes, which is not true. By any criterion, the Gregorian calendar is substantially more accurate than the 1 day in 128 years error of the Julian calendar (average year 365.25 days).

What is the approximate error for every 3,300 years?
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A:
one day