Copulas
n. 系动词（如be,seem,appear等）, （命题主词与谓词间的）连系( copula的复数形式 )
🗣️ 情景例句
I think it's about time we got going.
我想差不多是告辞的时候了。
Please bring me a glass.
请给我一杯。
How long has Kate been at her school?
凯特进校学习有多长时间了？