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 would an engine driver have to do to adjust the more modern type of valve?, Context: Steam engines frequently possess two independent mechanisms for ensuring that the pressure in the boiler does not go too high; one may be adjusted by the user, the second is typically designed as an ultimate fail-safe. Such safety valves traditionally used a simple lever to restrain a plug valve in the top of a boiler. One end of the lever carried a weight or spring that restrained the valve against steam pressure. Early valves could be adjusted by engine drivers, leading to many accidents when a driver fastened the valve down to allow greater steam pressure and more power from the engine. The more recent type of safety valve uses an adjustable spring-loaded valve, which is locked such that operators may not tamper with its adjustment unless a seal illegally is broken. This arrangement is considerably safer.[citation needed]

A: seal illegally is broken
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Q: Who was related to each other?, Context: The next direct threat to Temüjin was the Naimans (Naiman Mongols), with whom Jamukha and his followers took refuge. The Naimans did not surrender, although enough sectors again voluntarily sided with Temüjin. In 1201, a khuruldai elected Jamukha as Gür Khan, "universal ruler", a title used by the rulers of the Qara Khitai. Jamukha's assumption of this title was the final breach with Temüjin, and Jamukha formed a coalition of tribes to oppose him. Before the conflict, however, several generals abandoned Jamukha, including Subutai, Jelme's well-known younger brother. After several battles, Jamukha was finally turned over to Temüjin by his own men in 1206.

A:
Subutai, Jelme
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