Given a question and a context passage, generate the answer having the word or phrase from the context passage. Here, the answer should be a shortest continous span from the passage.
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Question: Context: The smallest planet, Mercury, is the planet closest to the Sun. Because Mercury is so close to the Sun, it is difficult to observe from Earth, even with a telescope. However, the Mariner 10 spacecraft, shown in Figure 1.1, visited Mercury from 1974 to 1975. The MESSENGER spacecraft has been studying Mercury in detail since 2005. The craft is currently in orbit around the planet, where it is creating detailed maps. MESSENGER stands for Mercury Surface, Space Environment, Geochemistry and Ranging. (a) Mariner 10 made three flybys of Mercury in 1974 and 1975. (b) A 2008 image of compiled from a flyby by MESSENGER. As Figure 1.2 shows, the surface of Mercury is covered with craters, like Earths Moon. Ancient impact craters means that for billions of years Mercury hasnt changed much geologically. Also, with very little atmosphere, the processes of weathering and erosion do not wear down structures on the planet. Mercury is named for the Roman messenger god, who could run extremely quickly, just as the planet moves very quickly in its orbit around the Sun. A year on Mercury the length of time it takes to orbit the Sun is just 88 Earth days. Despite its very short years, Mercury has very long days. A day is defined as the time it takes a planet to turn on its axis. Mercury rotates slowly on its axis, turning exactly three times for every two times it orbits the Sun. Therefore, each day on Mercury is 57 Earth days long. In other words, on Mercury, a year is only a Mercury day and a half long! Mercury is close to the Sun, so it can get very hot. However, Mercury has virtually no atmosphere, no water to insulate the surface, and it rotates very slowly. For these reasons, temperatures on the surface of Mercury vary widely. In direct sunlight, the surface can be as hot as 427 C (801 F). On the dark side, or in the shadows inside craters, the surface can be as cold as -183 C (-297 F)! Although most of Mercury is extremely dry, scientists think Mercury is covered with craters, like Earths Moon. MESSENGER has taken extremely detailed pictures of the planets surface. there may be a small amount of water in the form of ice at the poles of Mercury, in areas that never receive direct sunlight. Figure 1.3 shows a diagram of Mercurys interior. Mercury is one of the densest planets. Its relatively large, liquid core, made mostly of melted iron, takes up about 42% of the planets volume. 
 Question: the core of mercury is made mostly of melted

Answer: iron


Question: Context: The military aspect of the war began with the Armistice of Mudros. The military operations of the Greco-Turkish war can be roughly divided into three main phases: the first phase, spanning the period from May 1919 to October 1920, encompassed the Greek Landings in Asia Minor and their consolidation along the Aegean Coast. The second phase lasted from October 1920 to August 1921, and was characterised by Greek offensive operations. The third and final phase lasted until August 1922, when the strategic initiative was held by the Turkish Army. 
 Question: What was the shortest phase of the war?

Answer: the second phase


Question: Context: German submarine U-331 was a Type VIIC U-boat of Nazi Germany's Kriegsmarine during World War II. The submarine was laid down on 26 January 1940 at the Nordseewerke yard at Emden, launched on 20 December 1940, and commissioned on 31 March 1941 under the command of Oberleutnant zur See Hans-Diedrich Freiherr von Tiesenhausen. 
 Question: What company made German submarine U-331?

Answer:
nordseewerke