Problem: One of the most spectacular examples of obligate mutualism is between the siboglinid tube worms and symbiotic bacteria that live at hydrothermal vents and cold seeps. The worm has no digestive tract and is wholly reliant on its internal symbionts for nutrition. The bacteria oxidize either hydrogen sulfide or methane, which the host supplies to them. These worms were discovered in the late 1980s at the hydrothermal vents near the Galapagos Islands and have since been found at deep-sea hydrothermal vents and cold seeps in all of the world's oceans.
When were the symbiotic bacteria discovered?
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Answer: unanswerable


Problem: World War II (1939-1945) devastated the country's economy, but the high levels of economic growth that followed from 1950 to 1980 have been called the Greek economic miracle. From 2000 Greece saw high levels of GDP growth above the Eurozone average, peaking at 5.8% in 2003 and 5.7% in 2006. The subsequent Great Recession and Greek government-debt crisis, a central focus of the wider European debt crisis, plunged the economy into a sharp downturn, with real GDP growth rates of −0.3% in 2008, −4.3% in 2009, −5.5% in 2010, −9.1% in 2011, −7.3% in 2012 and −3.2% in 2013. In 2011, the country's public debt reached €356 billion (172% of nominal GDP). After negotiating the biggest debt restructuring in history with the private sector, Greece reduced its sovereign debt burden to €280 billion (137% of GDP) in the first quarter of 2012. Greece achieved a real GDP growth rate of 0.7% in 2014 after 6 years of economic decline, but fell back into recession in 2015.
What years of economic growth was called Greece's economic miracle?
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Answer: 1950 to 1980


Problem: The Quran and Muhammad talked about racial equality and justice as in The Farewell Sermon. Tribal and nationalistic differences were discouraged. But after Muhammad's passing, the old tribal differences between the Arabs started to resurface. Following the Roman–Persian Wars and the Byzantine–Sassanid Wars, deep rooted differences between Iraq, formally under the Persian Sassanid Empire, and Syria, formally under the Byzantine Empire, also existed. Each wanted the capital of the newly established Islamic State to be in their area. Previously, the second caliph Umar was very firm on the governors and his spies kept an eye on them. If he felt that a governor or a commander was becoming attracted to wealth, he had him removed from his position.
Who was the second caliph?
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Answer:
Umar