Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.

Q: Einsteinium was discovered as a component of the debris of the first hydrogen bomb explosion in 1952, and named after Albert Einstein.

A: When was Einsteinium first discovered?
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Q: The Canon de 75 mle TR was a field gun used by Belgium during World War I and World War II. It was a license-built copy of the Krupp M 1905 gun.

A: What year was Canon de 75 mle TR made?
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Q: Human population growth over the past 10,000 years has been tremendous (Figure 1.1). The entire human popula- tion was estimated to be 5 million in 8000 B.C. 300 million in A.D. 1 1 billion in 1802 3 billion in 1961 7 billion in 2011 As the human population continues to grow, different factors limit population in different parts of the world. What might be a limiting factor for human population in a particular location? Space, clean air, clean water, and food to feed everyone are limiting in some locations. Not only has the population increased, but the rate of population growth has increased (Figure 1.2). The population was estimated to reach 7 billion in 2012, but it did so in 2011, just 12 years after reaching 6 billion. Human population from 10,000 BC through 2000 AD, showing the exponential increase in human population that has occurred in the last few centuries. The amount of time between the addition of each one billion people to the planets population, including speculation about the future. Although population continues to grow rapidly, the rate that the growth rate is increasing has declined. Still, a recent estimate by the United Nations estimates that 10.1 billion people will be sharing this planet by the end of the century. The total added will be about 3 billion people, which is more than were even in existence as recently as 1960.

A:
human population reached its first billion in which year?
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