This task is about writing a correct answer for the reading comprehension task. Based on the information provided in a given passage, you should identify the shortest continuous text span from the passage that serves as an answer to the given question. Avoid answers that are incorrect or provides incomplete justification for the question.

Q: Passage: The crew of Apollo 8 sent the first live televised pictures of the Earth and the Moon back to Earth, and read from the creation story in the Book of Genesis, on Christmas Eve, 1968. An estimated one-quarter of the population of the world saw—either live or delayed—the Christmas Eve transmission during the ninth orbit of the Moon. The mission and Christmas provided an inspiring end to 1968, which had been a troubled year for the US, marked by Vietnam War protests, race riots, and the assassinations of civil rights leader Martin Luther King, Jr., and Senator Robert F. Kennedy. Question: How much of the population of Earth ended up seeing the images of the Earth and the Moon?

A: one-quarter of the population
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Q: Passage: From 1920, Eisenhower served under a succession of talented generals – Fox Conner, John J. Pershing, Douglas MacArthur and George Marshall. He first became executive officer to General Conner in the Panama Canal Zone, where, joined by Mamie, he served until 1924. Under Conner's tutelage, he studied military history and theory (including Carl von Clausewitz's On War), and later cited Conner's enormous influence on his military thinking, saying in 1962 that "Fox Conner was the ablest man I ever knew." Conner's comment on Eisenhower was, "[He] is one of the most capable, efficient and loyal officers I have ever met." On Conner's recommendation, in 1925–26 he attended the Command and General Staff College at Fort Leavenworth, Kansas, where he graduated first in a class of 245 officers. He then served as a battalion commander at Fort Benning, Georgia, until 1927. Question: What role did Eisenhower serve under Fox Conner?

A: executive officer
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Q: Passage: Time is one of the seven fundamental physical quantities in both the International System of Units and International System of Quantities. Time is used to define other quantities—such as velocity—so defining time in terms of such quantities would result in circularity of definition. An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, is highly useful in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called spacetime bring questions about space into questions about time, questions that have their roots in the works of early students of natural philosophy. Question: What is an example of a quantity that time is used to define, mentioned in the paragraph?

A:
velocity
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