Pentafluorination
五氟化反應
??? 情景例句
We have closely connected with firms in USA.
我們同美國有良好的業務關系。
What's your nationality? Are you an American.
你的國籍是什么？你是美國人？
We had lost the path and had no hope of finding it again.
我們找不到那條小路，而且也沒有希望再找到它了。