In this task, you are given a question and a context passage. You have to answer the question based on the given passage.

Q: What is Rayleigh scattering?, Context: In nature, the red color of blood comes from hemoglobin, the iron-containing protein found in the red blood cells of all vertebrates. The red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars. The red sky at sunset and sunrise is caused by an optical effect known as Rayleigh scattering, which, when the sun is low or below the horizon, increases the red-wavelength light that reaches the eye. The color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the human population has red hair; the color is produced by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin.

A: optical effect
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Q: The expansion of what further cemented Houston's emergence as a powerhouse commercial city?, Context: By 1860, Houston had emerged as a commercial and railroad hub for the export of cotton. Railroad spurs from the Texas inland converged in Houston, where they met rail lines to the ports of Galveston and Beaumont. During the American Civil War, Houston served as a headquarters for General John Bankhead Magruder, who used the city as an organization point for the Battle of Galveston. After the Civil War, Houston businessmen initiated efforts to widen the city's extensive system of bayous so the city could accept more commerce between downtown and the nearby port of Galveston. By 1890, Houston was the railroad center of Texas.

A: bayous
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Q: What was improved due to the better recording technology?, Context: Whether there are measurable changes in the sea level relative to the islands of Tuvalu is a contentious issue. There were problems associated with the pre-1993 sea level records from Funafuti which resulted in improvements in the recording technology to provide more reliable data for analysis. The degree of uncertainty as to estimates of sea level change relative to the islands of Tuvalu was reflected in the conclusions made in 2002 from the available data. The 2011 report of the Pacific Climate Change Science Program published by the Australian Government, concludes: "The sea-level rise near Tuvalu measured by satellite altimeters since 1993 is about 5 mm (0.2 in) per year."

A:
data
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