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

Q: How does a chestnut tree form its heartwood?, Context: The term heartwood derives solely from its position and not from any vital importance to the tree. This is evidenced by the fact that a tree can thrive with its heart completely decayed. Some species begin to form heartwood very early in life, so having only a thin layer of live sapwood, while in others the change comes slowly. Thin sapwood is characteristic of such species as chestnut, black locust, mulberry, osage-orange, and sassafras, while in maple, ash, hickory, hackberry, beech, and pine, thick sapwood is the rule. Others never form heartwood.

A: the change comes slowly
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Q: What vehicle could you have that you would need lower pressure boiler feed water?, Context: The Rankine cycle and most practical steam engines have a water pump to recycle or top up the boiler water, so that they may be run continuously. Utility and industrial boilers commonly use multi-stage centrifugal pumps; however, other types are used. Another means of supplying lower-pressure boiler feed water is an injector, which uses a steam jet usually supplied from the boiler. Injectors became popular in the 1850s but are no longer widely used, except in applications such as steam locomotives.

A: steam locomotives
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Q: What depleted the inhabitants?, Context: Intermittent warfare lasting from July 23, 1670 until July 1695, plus the typhoons of 1671 and 1693, and in particular the smallpox epidemic of 1688, reduced the Chamorro population from 50,000 to 10,000 to less than 5,000.:86 Precipitated by the death of Quipuha, and the murder of Father San Vitores and Pedro Calungsod by local rebel chief Matapang, tensions led to a number of conflicts. Captain Juan de Santiago started a campaign to pacify the island, which was continued by the successive commanders of the Spanish forces.:68–74

A:
smallpox
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