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: When a new moon passes directly between the Earth and the Sun, it causes a solar eclipse (Figure 24.20). The Moon casts a shadow on the Earth and blocks our view of the Sun. This happens only all three are lined up and in the same plane. This plane is called the ecliptic. The ecliptic is the plane of Earths orbit around the Sun. The Moons shadow has two distinct parts. The umbra is the inner, cone-shaped part of the shadow. It is the part in which all of the light has been blocked. The penumbra is the outer part of Moons shadow. It is where the light is only partially blocked. When the Moons shadow completely blocks the Sun, it is a total solar eclipse (Figure 24.21). If only part of the Sun is out of view, it is a partial solar eclipse. Solar eclipses are rare events. They usually only last a few minutes. That is because the Moons shadow only covers a very small area on Earth and Earth is turning very rapidly. Solar eclipses are amazing to experience. It appears like night only strange. Birds may sing as they do at dusk. Stars become visible in the sky and it gets colder outside. Unlike at night, the Sun is out. So during a solar eclipse, its easy to see the Suns corona and solar prominences. This NASA page will inform you on when solar eclipses are expected: [Link] Sometimes a full moon moves through Earths shadow. This is a lunar eclipse (Figure 24.22). During a total lunar eclipse, the Moon travels completely in Earths umbra. During a partial lunar eclipse, only a portion of the Moon enters Earths umbra. When the Moon passes through Earths penumbra, it is a penumbral eclipse. Since Earths shadow is large, a lunar eclipse lasts for hours. Anyone with a view of the Moon can see a lunar eclipse. Partial lunar eclipses occur at least twice a year, but total lunar eclipses are less common. The Moon glows with a dull red coloring during a total lunar eclipse. The Moon does not produce any light of its own. It only reflects light from the Sun. As the Moon moves around the Earth, we see different parts of the Moon lit up by the Sun. This causes the phases of the Moon. As the Moon revolves around Earth, it changes from fully lit to completely dark and back again. A full moon occurs when the whole side facing Earth is lit. This happens when Earth is between the Moon and the Sun. About one week later, the Moon enters the quarter-moon phase. Only half of the Moons lit surface is visible from Earth, so it appears as a half circle. When the Moon moves between Earth and the Sun, the side facing Earth is completely dark. This is called the new moon phase. Sometimes you can just barely make out the outline of the new moon in the sky. This is because some sunlight reflects off the Earth and hits the Moon. Before and after the quarter-moon phases are the gibbous and crescent phases. During the crescent moon phase, the Moon is less than half lit. It is seen as only a sliver or crescent shape. During the gibbous moon phase, the Moon is more than half lit. It is not full. The Moon undergoes a complete cycle of phases about every 29.5 days.
Question: phase of the moon in which the entire side facing Earth is dark
[A]: new moon

[Q]: Context: Pat came over from Ireland to England with his wife one year ago to find work. He got quite a good job with a building company, and as he did not drink or smoke, he saved up quite a lot of money. His wife's parents were still in Ireland, and one day she got a telegram saying that her mother was ill, so Pat gave her some money and she went to Ireland to see her mother. After a week, Pat wanted to write a letter to her, but he could not read or write very well, so he went to his priest and asked him to do it for him. Pat told the priest what he wanted to say, and the priest wrote it down. After a few minutes Pat stopped, and the priest said," Do you want to say more?" "Only ," 'Please excuse the bad writing and spelling'," Pat said.
Question: Who really made a mistake in the story?
[A]: pat.

[Q]: Context: Radioactive decay is the breakdown of unstable elements into stable elements. To understand this process, recall that the atoms of all elements contain the particles protons, neutrons, and electrons. An element is defined by the number of protons it contains. All atoms of a given element contain the same number of protons. The number of neutrons in an element may vary. Atoms of an element with different numbers of neutrons are called isotopes. Consider carbon as an example. Two isotopes of carbon are shown in Figure 11.15. Compare their protons and neutrons. Both contain 6 protons. But carbon-12 has 6 neutrons and carbon-14 has 8 neutrons. Almost all carbon atoms are carbon-12. This is a stable isotope of carbon. Only a tiny percentage of carbon atoms are carbon-14. Carbon-14 is unstable. Figure 11.16 shows carbon dioxide, which forms in the atmosphere from carbon-14 and oxygen. Neutrons in cosmic rays strike nitrogen atoms in the atmosphere. The nitrogen forms carbon- 14. Carbon in the atmosphere combines with oxygen to form carbon dioxide. Plants take in carbon dioxide during photosynthesis. In this way, carbon-14 enters food chains. Like other unstable isotopes, carbon-14 breaks down, or decays. For carbon-14 decay, each carbon-14 atom loses an alpha particle. It changes to a stable atom of nitrogen-14. This is illustrated in Figure 11.17. The decay of an unstable isotope to a stable element occurs at a constant rate. This rate is different for each isotope pair. The decay rate is measured in a unit called the half-life. The half-life is the time it takes for half of a given amount of an isotope to decay. For example, the half-life of carbon-14 is 5730 years. Imagine that you start out with 100 grams of carbon-14. In 5730 years, half of it decays. This leaves 50 grams of carbon-14. Over the next 5730 years, half of the remaining amount will decay. Now there are 25 grams of carbon-14. How many grams will there be in another 5730 years? Figure 11.18 graphs the rate of decay of carbon-14. The rate of decay of unstable isotopes can be used to estimate the absolute ages of fossils and rocks. This type of dating is called radiometric dating. The best-known method of radiometric dating is carbon-14 dating. A living thing takes in carbon-14 (along with stable carbon-12). As the carbon-14 decays, it is replaced with more carbon-14. After the organism dies, it stops taking in carbon. That includes carbon-14. The carbon-14 that is in its body continues to decay. So the organism contains less and less carbon-14 as time goes on. We can estimate the amount of carbon-14 that has decayed by measuring the amount of carbon-14 to carbon-12. We know how fast carbon-14 decays. With this information, we can tell how long ago the organism died. Carbon-14 has a relatively short half-life. It decays quickly compared to some other unstable isotopes. So carbon- 14 dating is useful for specimens younger than 50,000 years old. Thats a blink of an eye in geologic time. But radiocarbon dating is very useful for more recent events. One important use of radiocarbon is early human sites. Carbon-14 dating is also limited to the remains of once-living things. To date rocks, scientists use other radioactive isotopes. The isotopes in Table 11.1 are used to date igneous rocks. These isotopes have much longer half-lives than carbon- 14. Because they decay more slowly, they can be used to date much older specimens. Which of these isotopes could be used to date a rock that formed half a million years ago? Unstable Isotope Decays to At a Half-Life of (years) Potassium-40 Uranium-235 Uranium-238 Argon-40 Lead-207 Lead-206 1.3 billion 700 million 4.5 billion Dates Rocks Aged (years old) 100 thousand - 1 billion 1 million - 4.5 billion 1 million - 4.5 billion
Question: using radioactive decay to estimate the age of a fossil or rock
[A]:
radiometric dating