氧化亚氮与氧混合气体全麻时，氧浓度最佳为()A．10%～20% B．30%～40%

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问题单项选择题 A3/A4型题

氧化亚氮与氧混合气体全麻时，氧浓度最佳为()

A．10%～20%

B．30%～40%

C．40%～50%

D．50%～60%

E．20%～30%

答案

参考答案：C

填空题

根据句意和首字母提示补全单词.

1. Don't w________ water. Please turn off the cock after you wash your hands.

2. Gold, silver and iron are all m_______.

3. It's more and more important for everyone to save e_______ now.

4. Air p_______ is quite harmful to our health.

5.The students from a green school are helping collect waste paper and bottles for r________.

判断题

吸引外资，关键是要创造良好的投资环境，包括硬环境和软环境。发展中国家经济落后，基础工业较差，所以最重要的是改善硬环境。