youdao

If an unknown person enters a home, the camera will send the owner a warning that will cause an alarm to sound on the owner's smartphone.

如果一个不知名的人进入家中，摄像头就会向主人发送警告，并在主人的智能手机上响起警报。

youdao

When most of us get a text message on our cell phone from an unknown person, we usually say "sorry, wrong number!"

当我们收到陌生人的短信时, 我们通常会说：“对不起, 你发错了！”

youdao

At the time he was an unknown person who worked in the patent bureau in Berne.

UNESCO: Culture

An unknown person once said that high school is the mouse race to prepare you for the rat race.

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But information about ethnic background can also refine descriptions of an unknown person.

BBC: Painting a suspect's portrait with DNA