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.

Q: Context: Energy from the Sun comes from the lightest element, hydrogen, fusing together to create the second lightest element, helium. Nuclear fusion on the Sun releases tremendous amounts of solar energy. The energy travels to the Earth, mostly as visible light. The light carries the energy through the empty space between the Sun and the Earth as radiation. Solar energy has been used for power on a small scale for hundreds of years, and plants have used it for billions of years. Unlike energy from fossil fuels, which almost always come from a central power plant or refinery, solar power can be harnessed locally (Figure 1.1). A set of solar panels on a homes rooftop can be used to heat water for a swimming pool or can provide electricity to the house. Societys use of solar power on a larger scale is just starting to increase. Scientists and engineers have very active, ongoing research into new ways to harness energy from the Sun more efficiently. Because of the tremendous amount of incoming sunlight, solar power is being developed in the United States in southeastern California, Nevada, and Arizona. Solar panels supply power to the Interna- tional Space Station. Solar power plants turn sunlight into electricity using a large group of mirrors to focus sunlight on one place, called a receiver (Figure 1.2). A liquid, such as oil or water, flows through this receiver and is heated to a high temperature by the focused sunlight. The heated liquid transfers its heat to a nearby object that is at a lower temperature through a process called conduction. The energy conducted by the heated liquid is used to make electricity. This solar power plant uses mirrors to focus sunlight on the tower in the center. The sunlight heats a liquid inside the tower to a very high temperature, producing energy to make electricity. Solar energy has many benefits. It is extremely abundant, widespread, and will never run out. But there are problems with the widespread use of solar power. Sunlight must be present. Solar power is not useful in locations that are often cloudy or dark. However, storage technology is being developed. The technology needed for solar power is still expensive. An increase in interested customers will provide incentive for companies to research and develop new technologies and to figure out how to mass-produce existing technologies (Figure 1.3). Solar panels require a lot of space. Fortunately, solar panels can be placed on any rooftop to supply at least some of the power required for a home or business. This experimental car is one example of the many uses that engineers have found for solar energy. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL: 
 Question: the source of solar power is nuclear

A: fusion.
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Q: Context: Coming off their last-second victory over the Bengals, the Broncos would play their Week 2 home opener against the Cleveland Browns. In the first quarter, Denver would trail early as Browns kicker Phil Dawson got a 22-yard field goal. Afterwards, the Broncos took the lead as quarterback Kyle Orton completed a 2-yard touchdown pass to tight end Tony Scheffler. Cleveland would creep close as Dawson made a 47-yard field goal, but Denver would answer as kicker Matt Prater got a 23-yard field goal in the second quarter and a 38-yard field goal in the third quarter. In the fourth, the Broncos pulled away as fullback Peyton Hillis got a 2-yard touchdown run and running back Correll Buckhalter got a 45-yard touchdown run. 
 Question: Which team scored the first touchdown?

A: broncos
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Q: 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: The scientist who discovered radioactivity was

A:
becquerel.
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