Qac
abbr. quaternary ammonium compound 季铵化合物（杀菌剂）
🗣️ 情景例句
It's too hard to explain.
这很难解释清楚。
Congratulations on your success.
我恭喜你成功了。
That's why I've come to see you.
这就是我来见您的原因。