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: Sport forms an integral part of German life, as demonstrated by the fact that 27 million Germans are members of a sports club and an additional twelve million pursue such an activity individually. Football is by far the most popular sport, and the German Football Federation (Deutscher Fußballbund) with more than 6.3 million members is the largest athletic organisation in the country. It also attracts the greatest audience, with hundreds of thousands of spectators attending Bundesliga matches and millions more watching on television. Question: How many Germans are members of sports clubs?

A: 27 million
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Q: Passage: Because of the acceptance of miscegenation, Brazil has avoided the binary polarization of society into black and white. In addition, it abolished slavery without a civil war. The bitter and sometimes violent racial tensions that have divided the US are notably absent in Brazil. According to the 2010 census, 6.7% of Brazilians said they were black, compared with 6.2% in 2000, and 43.1% said they were racially mixed, up from 38.5%. In 2010, Elio Ferreira de Araujo, Brazil's minister for racial equality, attributed the increases to growing pride among his country's black and indigenous communities. Question: How do the US and Brazil vary after slavery has ended?

A: violent racial tensions that have divided the US are notably absent in Brazil.
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Q: Passage: In 2004, NIST researchers presented evidence that an isotropic non-crystalline metallic phase (dubbed "q-glass") could be grown from the melt. This phase is the first phase, or "primary phase," to form in the Al-Fe-Si system during rapid cooling. Interestingly, experimental evidence indicates that this phase forms by a first-order transition. Transmission electron microscopy (TEM) images show that the q-glass nucleates from the melt as discrete particles, which grow spherically with a uniform growth rate in all directions. The diffraction pattern shows it to be an isotropic glassy phase. Yet there is a nucleation barrier, which implies an interfacial discontinuity (or internal surface) between the glass and the melt. Question: What shows that there is an inner surface between glass and melt?

A:
nucleation barrier
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