问题
单项选择题
综合安全技术
发生燃烧和火灾必须同时具备的条件是( )。
A．氧化剂、明火、点火源
B．氧化剂、可燃物、点火源
C．氧化剂、可燃物、木材
D．阻燃剂、可燃物、点火源
答案
参考答案：B
解析：同时具备氧化剂、可燃物、点火源，即火的三要素。这三个要素中缺少任何一个，燃烧都不能发生和维持，因此火的三要素是燃烧的必要条件。
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综合安全技术
发生燃烧和火灾必须同时具备的条件是( )。
A．氧化剂、明火、点火源
B．氧化剂、可燃物、点火源
C．氧化剂、可燃物、木材
D．阻燃剂、可燃物、点火源
参考答案：B
解析：同时具备氧化剂、可燃物、点火源，即火的三要素。这三个要素中缺少任何一个，燃烧都不能发生和维持，因此火的三要素是燃烧的必要条件。
My friends and I had just finished lunch at a hotel when it started to pour heavily. When it became lighter, I decided to brave the rain(冒雨) to get my , which was parked at my office three streets away. My friends argued that I shouldn’t go, mainly I was seven months pregnant (怀孕的) then. I told them that I’d be very . One of them wanted to come with me but I insisted that she should stay with another friend who needed with her baby.  I walked out of the and started making my way to the car. At the traffic crossing，a car stopped and the passenger with an umbrella. I knew what was happening, he walked right beside me and told me he’d send me to my destination(目的地). I was very embarrassed(尴尬的) and refused, he insisted on offering me his help. During our walk, he kept telling me to walk slower, as the ground was . When we got to the car parking lot, I him and we parted(分手). I did not get his and may not even recognize(认识) him now. Did he purposely stop for me? I’ll never know. So how did I pay it forward? I was at home when I two Indian construction(建筑) workers walking in the heavy rain. They were probably on their way to the construction sitenear my home, which was a long walk. I went out and them an umbrella. The two men were wet through. They were surprised by my action , and I told them they should the umbrella and keep it. They were very . And like me, probably wondered why a stranger was giving such kindness.
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