下列说法正确的是（） A．只要温度达到着火点，物质就会燃_爱下问搜题

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问题选择题

下列说法正确的是（　　）

A．只要温度达到着火点，物质就会燃烧

B．爆炸不一定是化学反应

C．任何物质燃烧的火焰都可以用水扑灭

D．着火点就是物质开始燃烧的地方

答案

A、物质燃烧需要达到燃烧的条件，这些条件必须同时具备，故此选项错误．

B、有一些物理变化的爆炸同样存在，如高压锅炉的爆炸，故此选项正确．

C、油着火以后一般用水不能扑灭，故此选项错误．

D、着火点是物质燃烧的最低温度，故此选项错误．

故选B

完形填空

One sunny afternoon, a seven-year-old girl went for a walk．She crossed a large area of grassland into the woods before she realized that she was lost．
Sitting on a rock and __41 what to do, she began crying．After a while, she__42__ to walk along a wide path lined with tall trees and thick bushes．When it was getting dark, she saw a small, dark wooden house．She opened the door and __43__ stepped in．Suddenly, she heard a strange noise, and she ran out of the door and back to the __44__．Cold and tired, she fell asleep near a __45_．
The girl’s parents were out and her dog, Laddy, was at home．Laddy __46__ that his mistrees（女主人）was in danger．He jumped through a window, breaking the glass．He looked in the fields．But he couldn’t find his mistress anywhere．However, from the ground came a __47__ scent (气味) as he lowered his head．He __48__ the scent and walked across the grassland．Barking loudly into the air, the dog _49__ through the woods until he found the __50_．But the girl was not there, so he headed back to the woods．Much to his __51__ , he saw his mistress’ blue shirt in the distance．He jumped over some bushes and saw the little stream, where the girl was __52__．
When she opened her eyes and 53 her dog standing beside her, the girl said, “you 54 me, Laddy,” and she kissed him several times．Seeing their daughter and dog coming back, the parents burst into tears of 55 ．That night Laddy had a heror’s supper: a huge meal of steak

C．remembering

D．unwillingly

A．satisfaction

C．disappointment

D．embarrassment

单项选择题

电流互感器在运行中必须使（）。

A.铁芯及二次线圈牢固接地

B.铁心两点接地

C.二次线圈不接地