正确答案: A

氧气是无色无味的无毒气体  氧气可以燃烧 吸氧为人体呼吸提供了适量的氧气 氧气可以支持燃烧

题目：有一位同学暑假去西藏发生了严重的高原反应，医生让他吸氧后症状缓解。吸氧可以帮人克服高原反应的原因是（      ）

解析：C

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举一反三的答案和解析：

[单选题]BOne day Mrs Wilson went shopping with Tracy and Ben． They went to the supermarket in the new shopping centre．“Why do you buy things here? Tracy wanted to know． "Because they are cheaper here than at the corner store near our home，”Mrs Wilson said． "Help me check the prices， please． "The Wilsons were not rich and Mrs Wilson was always careful with her money． She looked carefully at the prices of things． She bought lots of things in the supermarket． When they got home， the children said， "We don-t think you saved money by going to the supermar-ket． ""Of course I did，"Mrs Wilson said． "Everything was cheaper there．"We know，"the children said， "but we came home by taxi because we had too much to carry． The taxi fare was more than the money that you saved! Well done，"she said． "Next time we'll do the shopping nearby．

more expensive

解析：26.C【解析】由第二段第二句可推断。

[单选题]世界上人们共同使用的阿拉伯数字本不是阿拉伯人发明的，请问它是由什么人发明的 （ ）

印度人

[单选题]Thebesttitleforthepassageis______.

ReachingtheTopoftheMountain