Op. cit.
abbr. 前面引用的书(in the work already quoted)
🗣️ 情景例句
It is OK to ask children how old they are.
问小孩多大了是可以的。
Thank you for coming to see me off.
谢谢你来为我送行。
I am ready to sign the agreement.
我已经准备好了签合同。