Polyfluorination
多氟化反应
🗣️ 情景例句
This has been a hard course for me.
这门课对于我来说很难。
This is my friend Susan.
这位是我的朋友苏珊。
I'm poor, but I always enjoy myself! he said. I don't know why!
“我很穷，但我总是过得很愉快！”他说，“我不懂为什么！”