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
What's so special about him?
他有什么特别的呢？
Are you clear in your own mind what you ought to do.
你自己是否清楚该做什么？
the other the lack of freedom of the individual research worker.
二是研究人员缺乏个人自由。