问题
选择题
空气中体积约占1/5的气体是（ ）
A．氧气
B．氮气
C．稀有气体
D．二氧化碳
答案
空气中氧气大约占了空气总体积的21%，约1/5．
故选A．
搜题请搜索小程序“爱下问搜题”
空气中体积约占1/5的气体是（ ）
A．氧气
B．氮气
C．稀有气体
D．二氧化碳
空气中氧气大约占了空气总体积的21%，约1/5．
故选A．
| 根据对话内容，从方框内所给的选项中选出最佳选项，补全对话。 | |
| W: Hello? M: Hello! This is Mark. 1_______ W: Yes, this is Sandy. Anything new? M: It's weekend tomorrow. Shall we go for a spring touring? W: Sounds great! 2_______ M: What about the Yellowstone Park? They say the sights there are most beautiful this time of the season. W: Good! 3_______ M: Well, we can fish, camp and have a picnic. We'll do a lot of walking. Too. 4_______ W: Sure. 5_______ M: I'll pick you up at about 7 tomorrow morning, OK? W: OK! See you! M: See you! | |
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