Principals
n. 负责人( principal的复数形式 ); [法律]本人; 主要的人（或物）
🗣️ 情景例句
The rural workforce has been flowing in to the cities ever since the open door policy was adopted.
自从改革开放政策实施以来，农付劳动力正不断流向城市。
Someone is working in the manhole.
有人在
Yes, that's right.
是的。