有一种肉眼看不见的力量在起作用。

There is an ___unseen force at work that the naked eye cannot detect.

探险队发现了一个前所未见的洞穴系统。

The expedition discovered an ___unseen cave system.

她声称能够感知到那些肉眼看不见的存在。

She claimed to sense the presence of ___unseen beings.