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.

Example Input: Context: An electric transformer is a device that uses electromagnetic induction to change the voltage of electric current. Electromagnetic induction is the process of generating current with a magnetic field. It occurs when a magnetic field and electric conductor, such as a coil of wire, move relative to one another. A transformer may either increase or decrease voltage. You can see the basic components of an electric transformer in the Figure 1.1. Click image to the left or use the URL below. URL: The transformer in the diagram consists of two wire coils wrapped around an iron core. Each coil is part of a different circuit. When alternating current passes through coil P, it magnetizes the iron core. Because the current is alternating, the magnetic field of the iron core keeps reversing. This is where electromagnetic induction comes in. The changing magnetic field induces alternating current in coil S of the other circuit. Notice that coil P and coil S in the Figure 1.1 have the same number of turns of wire. In this case, the voltages of the primary and secondary currents are the same. Usually, the two coils of a transformer have different numbers of turns. In that case, the voltages of the two currents are different. When coil S has more turns than coil P, the voltage in the secondary current is greater than the voltage in the primary current (see Figure 1.2). This type of transformer is called a step-up transformer. Thats because it steps up, or increases, the voltage. When coil S has fewer turns of wire than coil P, the voltage in the secondary current is less than the voltage in the primary current (see Figure 1.3). This type of transformer is called a step-down transformer because it steps down, or decreases, the voltage. Q: Both step-up and step-down transformers are used in the electrical grid that carries electricity from a power plant to your home. Where in the grid do you think step-down transformers might be used? A: One place that step-down transformers are used is on the electric poles that supply current to homes. They reduce the voltage of the electric current before it enters home circuits. 
 Question: an electric transformer contains
Example Output: an iron core.

Example Input: Context: Meanwhile, in 1274, the former Dali Kingdom was officially reorganized as the Province of Yunnan, with Sayyid Ajjal Shams al-Din Omar as governor. In May 1275, the governor sent a report to the emperor stating that the embassy had not returned; that the Burmese evidently had no intention of submitting; and that war was the only way forward. But the emperor rejected an outright invasion. Just coming off a disastrous Japanese campaign, the emperor was unwilling to commit the central government troops to what he considered a low priority affair. He was now focused on delivering the final blow against the Song; the emperor ordered the Yunnan provincial army to secure the borderlands in order to block the escape path of the Song refugees. He also sanctioned a limited border war if Pagan contested the takeover. As planned, the Yunnan army proceeded to consolidate the borderlands in 1275-76. Elsewhere, the main Mongol armies had captured most of the Song territory by 1276. By 1277, at least one Burmese vassal state named "Gold Teeth" had submitted to the Mongols. Like in 1272, the Burmese government responded by sending an army to reclaim the rebellious state; but unlike in 1272, the Mongols had posted a sizable garrison there. Though it was ultimately under Mongol command, many of the officers and most of the soldiers of the garrison were Turkic-speaking peoples or people from the further west: Turks from Samarkand, Bukhara, Merv and Nishapur, but also captive soldiers from the Persian Khwarazmid empire, the Kipchaks, and even Bulgars from the lower Volga. 
 Question: Which happened first - the reorganization of the Province of Yunnan, or the capture of the Song territory?
Example Output: the province of yunnan

Example Input: Context: Radioactivity is the ability of an atom to emit, or give off, charged particles and energy from the nucleus. The charged particles and energy are called by the general term radiation. Only unstable nuclei emit radiation. When they do, they gain or lose protons. Then the atoms become different elements. (Be careful not to confuse this radiation with electromagnetic radiation, which has to do with the light given off by atoms as they absorb and then emit energy.) Radioactivity was discovered in 1896 by a French physicist named Antoine Henri Becquerel. Becquerel was experimenting with uranium, which glows after being exposed to sunlight. Becquerel wanted to see if the glow was caused by rays of energy, like rays of light and X-rays. He placed a bit of uranium on a photographic plate. The plate was similar to film thats used today to take X-rays. You can see an example of an X-ray in Figure 11.1. As Becquerel predicted, the uranium left an image on the photographic plate. This meant that uranium gives off rays after being exposed to sunlight. Becquerel was a good scientist, so he wanted to repeat his experiment to confirm his results. He placed more uranium on another photographic plate. However, the day had turned cloudy, so he tucked the plate and uranium in a drawer to try again another day. He wasnt expecting the uranium to leave an image on the plate without being exposed to sunlight. To his surprise, there was an image on the plate in the drawer the next day. Becquerel had discovered that uranium gives off rays without getting energy from light. He had discovered radioactivity, for which he received a Nobel prize. To learn more about the importance of Becquerels research, go to this URL: [Link] Another scientist, who worked with Becquerel, actually came up with the term "radioactivity." The other scientist was the French chemist Marie Curie. She went on to discover the radioactive elements polonium and radium. She won two Nobel Prizes for her discoveries. You can learn more about Marie Curie at this URL: [Link] Isotopes are atoms of the same element that differ from each other because they have different numbers of neutrons. Many elements have one or more isotopes that are radioactive. Radioactive isotopes are called radioisotopes. An example of a radioisotope is carbon-14. All carbon atoms have 6 protons, and most have 6 neutrons. These carbon atoms are called carbon-12, where 12 is the mass number (6 protons + 6 neutrons). A tiny percentage of carbon atoms have 8 neutrons instead of the usual 6. These atoms are called carbon-14 (6 protons + 8 neutrons). The nuclei of carbon-14 are unstable because they have too many neutrons. To be stable, a small nucleus like carbon, with just 6 protons, must have a 1:1 ratio of protons to neutrons. In other words, it must have the same number of neutrons as protons. In a large nucleus, with many protons, the ratio must be 2:1 or even 3:1 protons to neutrons. In elements with more than 83 protons, all the isotopes are radioactive (see Figure 11.2). The force of repulsion among all those protons overcomes the strong force holding them together. This makes the nuclei unstable and radioactive. Elements with more than 92 protons have such unstable nuclei that these elements do not even exist in nature. They exist only if they are created in a lab. A low level of radiation occurs naturally in the environment. This is called background radiation. It comes from various sources. One source is rocks, which may contain small amounts of radioactive elements such as uranium. Another source is cosmic rays. These are charged particles that arrive on Earth from outer space. Background radiation is generally considered to be safe for living things. A source of radiation that may be more dangerous is radon. Radon is a radioactive gas that forms in rocks underground. It can seep into basements and get trapped inside buildings. Then it may build up and become harmful to people who breathe it. Other sources of radiation are described in the interactive animation at this URL: [Link] You may have seen a sign like 
 Question: Uranium can leave an image on a photographic plate because uranium
Example Output:
is radioactive.