What are the fire triangle that the firefighters refer to?

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问题 What are the fire triangle that the firefighters refer to?
  
There are three conditions that need to be present in order for a wildfire to burn, which firefighters refer to as the fire triangle: fuel, oxygen, and a heat source. Fuel is any flammable material surrounding a fire, including trees, grasses, brush, even homes. The greater an area’s fuel load, the more intense the fire. Air supplies the oxygen a fire needs to burn. Heat sources help spark the wildfire and bring fuel to temperatures hot enough to ignite. Lightning, burning campfires or cigarettes, hot winds, and even the sun can all provide sufficient heat to spark a wildfire.
   Although four out of five wildfires are started by people, nature is usually more than happy to help fan the flames. Dry weather and drought convert green vegetation into bone-dry, flammable fuel; strong winds spread fire quickly over land; and warm temperatures encourage combustion. When these factors come together all that’s needed is a spark—in the form of lightning, arson, a downed power line, or a burning campfire or cigarette—to ignite a blaze that could last for weeks and consume tens of thousands of acres.
   These violent infernos occur around the world and in most of the 50 states, but they are most common in the U. S. West, where heat, drought, and frequent thunderstorms create perfect wildfire conditions. Montana, Idaho, Wyoming, Washington, Colorado, Oregon, and California experience some of the worst conflagrations in the U. S. In California wildfires are often made worse by the hot, dry Santa Ana winds, which can carry a spark for miles.
   Firefighters fight wildfires by depriving them of one or more of the fire triangle fundamentals. Traditional methods include water dousing and spraying fire retardants to extinguish existing fires. Clearing vegetation to create firebreaks starves a fire of fuel and can help slow or contain it. Firefighters also fight wildfires by deliberately starting fires in a process called controlled burning. These prescribed fires remove undergrowth, brush, and ground litter from a forest, depriving a wildfire of fuel.

选项 A、Thundering, burning cigarette ends and even the glass.
B、Lightning, burning campfires and even hot winds.
C、Burning cigarettes, hot winds and even the moon.
D、Hot winds, the sun and even thundering.

答案B

解析 根据原文“Heat sources…Lightning,burning campfires or cigarettes,hot winds,and even the sun…”判断,引起火灾的热源可能是闪电、篝火、烟头、热风等等,故本题应该选B。
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